An American movie takes place in a foreign land. Just to prove it to you, all the adults have an appropriate accent (or at least some kind of accent). Then a kid shows up speaking fluent American English, and unless the kid is a stellar actor, this can poke a hole in Suspension of Disbelief.
Truth in Television: With the pervasiveness of American media and the Internet, kids who grew up watching YouTube and Netflix will likely speak with American accents, especially if the child is less than 12 when their speech patterns aren't fully set. They will also likely adopt American English slang even in their own local languages which wouldn't be typical of someone who learned formal English back in the day only in their local school. Even afterward, a few people can adapt their accents and speech mannerisms, arriving in the US as late as 18 or 20 and managing to learn to speak English with flawless American accents.
However, this trope still appears in settings where it is not feasible for children to be exposed to American English, especially in fantasy settings without an American Fantasy Counterpart Culture. One effect is that it makes the children sound more innocent, at least to North American viewers, while the adults sound exotic and refined due to American accents being associated as a sort of default English.
Of course, this trope tends to appear more due to practical reasons - the vast majority of Hollywood's movies are filmed in California, and there are a number of laws involving child actors all around the world. Finding a kid who lives in or near Los Angeles just makes the situation a lot less complicated. And due to Hollywood's gravity, this effect bleeds into animation and video games as well.
- Robin Hood: Most of the adults have British accents, but all the kids have American ones.
- In How to Train Your Dragon, every single member of the parents' generation speaks with a Scottish accent. Every single member of Hiccup's speaks with an American one. Word of God is that this was intentional to make the younger generation more relatable to the western (read: American) audience and to underscore the divide between the traditionalist adults and the modern, progressive youth.
- An American Tail: The Mousekewitz family starts off in Russia, and while Mama and Papa have extremely thick Russian accents, Fievel and Tanya have American ones before they move to America.
- In Pinocchio, Geppetto (Christian Rub) has a foreign accent but Pinocchio (Dickie Jones) has a Midwestern American accent. Then again, Pinocchio was brought to life by a fairy of no terrestrial nationality.
- Disney has also inverted this trope, however. In Peter Pan, the Darling kids (with the exception of Michael) are practically the only characters with British accents. The same is true with Alice in Alice in Wonderland, though to a lesser extent. Some Wonderland characters sound English, but the most prominent ones sound American. (Incidentally, Alice and Wendy were voiced by the same British child actress, Kathryn Beaumont.)
- In The Aristocats, Duchess sounds Eastern European (voice actress Eva Gabor was Hungarian), while the kittens Toulouse and Berlioz sound American and Marie has a Mid-Atlantic/British accent, despite being natives of Paris, France.
- Simba in The Lion King (1994), in sharp contrast to his parents (although Mufasa has more of a "Mid-Atlantic" accent than a non-American one, and Sarabi's accent wobbles between American and Madge Sinclair's native Jamaican). Scar, his uncle, however, sounds British.
- The titular Moana is voiced by American Auli'i Cravalho, while many of the adults are played by actors from Australia or New Zealand. However, all of the lead actors are of Pacific Islander descent. It's not that noticeable since she speaks with a Hawaiian Pidgin accent as opposed to the Midwestern/Californian accent these teenage characters tend to have.
- In Beauty and the Beast, the enchanted objects uniformly have British or French accents (the story is set in France). The only exception is Chip, who speaks with an American accent despite his mother, Mrs. Potts, having the quintessential English matron's voice, Angela Lansbury. The live-action remake amended this.
- Downplayed in Dorothy Meets Ozma of Oz. Dorothy, Aunt Em, and Uncle Henry all have American accents, but Dorothy is the only one without a midwestern accent.
- The Sound of Music's film adaptation has the adult characters speaking in English accents. All the children speak with American accent - except Nicholas Hammond, who was the lone Brit among his on screen siblings.
- Both film adaptations of Charlie and the Chocolate Factory go with a Where the Hell Is Springfield? approach to the location of Charlie Bucket's home and Wonka's Factory, and this trope winds up being invoked in one version and inverted in another. In the 1971 film Willy Wonka & the Chocolate Factory, which was shot in Munich, Charlie and his family are amongst the only people in town with American accents while in the 2005 version Charlie and the Chocolate Factory, they're amongst the only ones with British accents.
- Inverted in Aliens: Everybody's American, but the one child occasionally slips into an English accent. This is due to her actress Carrie Henn, who was a Florida native, but was living in England at the time - and thus would slip between the two dialects. Both Newt's parents in the film speak with American accents, as does her brother (though he's played by her actual brother).
- Also inverted in Superman II, which was largely filmed in the UK. The few child characters who appear all have British accents, which is more glaring than usual because one is a kid from a hick town and the other two are a pair of streetwise black kids.
- In Jurassic Park, John Hammond is Scottish while his grandchildren are American. However, his company is apparently U.S.-based, so it's easy to imagine Lex and Tim were raised in America. But then in The Lost World, American actor Arliss Howard plays Hammond's adult nephew with an English accent...
- In the novel, Hammond is not specified to have any foreign accent, nor is he said to be foreign, period. Whereas Malcolm is subtly implied to be British; when he introduces himself, he says, "I do maths." Americans would more likely say "math." Perhaps the filmmakers picked up on this and inverted the apparent accents...
- This is inverted in The Kite Runner, which takes place partially in Afghanistan. The child actors were Afghan, but the adult cast was composed of Iranian, British and French actors. In fact, many of them had to learn Farsi for the part.
- In The Little Vampire, an American family moves to Scotland. Everyone there has Scottish accents except for the English-accented vampires.
- In Orson Welles's 1948 film adaptation of Macbeth, he had the cast affect Scottish accents (though the studio insisted on a separate audio track being recorded with American). The exception is Orson Welles's own daughter playing Macduff's young son. The other prominent child character Fleance has all his dialogue removed.
- Inverted with Queer as Folk: The American series was set in Pittsburgh, but filmed in Canada — the kid has a Canadian accent.
- Similarly inverted in Power Rangers Samurai, in which all the adults have American accents, but flashbacks of the Red and Gold Rangers have them as kids with New Zealand accents.
- A minor example from Lost: (Scottish) Desmond and (English) Penny's son, in one of his few lines, says "Mommy" instead of the British "Mummy". They're filming in Hawaii and can't exactly get a British 3-year old, so it gets a pass.
- Angel's son, Connor, was born in America but abducted when he was just a few weeks old. Connor grew up in a "Hell Dimension" with his only human contact being his "father"/abductee, who had an English accent. Connor's accent is, of course, American.
- Once Upon a Time:
- Rumpelstiltskin has a Scottish accent, his wife has an English accent, and their son Baelfire has an American accent. It's not so apparent since the kingdom is shown to have accents from all over the globe.
- Here's a weird one. Rumpelstiltskin's father Malcolm has a Scottish accent like his son but when he's restored to his younger self and becomes Peter Pan, the accent is English.
- A case where it happens with the same character! Geppetto in the present day speaks with an Italian accent. His child self however speaks with an American one. Even so, his son Pinocchio speaks with an American accent too - even when raised by an Italian-sounding parent.
- A variant in Shortland Street: The McKay parents are both Australian, but their teenage kids (who immigrated with them) are Kiwi.
- Avatar: The Last Airbender is a good example: None of the main, 12- to 16-year-old actors have non-American accents, but plenty of adults do: Iroh, played by Mako, has a Japanese accent, as does the warden from the episode "Imprisoned", played by George Takei. James Hong plays the mayor of Chin in season two, which also introduces the Foggy Swamp Water Tribe, whose members sound as if they hail from the Deep South. This is probably a Translation Convention, as they all write in traditional calligraphy.
- On the other hand, Sokka & Katara's, Toph's, and Zuko's parents all have American accents. Worth noting, however, is that Aang's Parental Substitute Gyatso has a Japanese accent.
- It's also worth noting that with a larger talent pool of adult actors the show is far more likely to cast Asians for the adult roles, even if they have American accents, like Daniel Dae Kim as general Fong or George Takei as the warden.
- Intentionally done in Gargoyles. The elderly Hudson has a thick Scottish accent while the rest of the clan range from American accents to neutral. This was done to highlight the generational differences and acceptances each had of the modern world. As the series progressed, more Clans living in Modern Times would be discovered (Specifically the English, Japanese, and Guatemalan clans) spoke in region appropriate accents. An explanation of the Avalon Clan (who all grew up with Scottish or English accented characters yet still spoke with an American accent) was never given.
- Jackie Chan Adventures: Both Jackie and Uncle have been living in America for years, but retain noticeable Chinese accents. Jade is fresh out of Hong Kong but speaks flawless American English.
- Some of the younger locomotives in Thomas the Tank Engine were given American accents in the later episodes, while some of the older locomotives were given British accents.
- Averted with the humans, however, where both the children and the adults, in that case, all have British accents.
- The newer engines were imported from America (or Canada) after the British locomotive industry went under?
- On Mike, Lu & Og, Lu and Og sound American compared to the adults' British accents. Subverted with Mike, who is American (specifically, from New York).
- Star vs. the Forces of Evil: Star and her parents are from Another Dimension. However, while they both have British accents (though they are played by American actors), Star's accent is American. Other people from Mewni have American accents, so it could be justified by Star's family being royalty, but that would still leave Star's accent unexplained.
- In Transformers Animated: Issac Sumdac has a Hindi accent, but his daughter Sari has an American one.
- Inverted with Child Prodigy Dexter from Dexter's Laboratory, who speaks with a vaguely Eastern European accent despite being 100% American like his parents. Likely a reference to the show's creator being a Russian immigrant to America as well as the fact that Russia and the rest of the Soviet Union produced a large number of renowned scientists.
- In Family Guy, Stewie inverts this. His family speaks with accents one might find from Rhode Island, while he speaks with something of a British accent (it's there but it's subtle), playing into the Evil Brit trope he was from earlier seasons. In a segment from the second Viewer Mail episode, he plays this straight, where his British counterpart speaks with an exaggerated Texan accent, while the rest of the family speaks with British accents. In "Send in Stewie, Please", it is revealed that Stewie had been faking his accent all along. When his therapist suggests that he speak in his normal voice and be like everyone else, Stewie reverts back to his British accent, since he does not want to be like everyone else.
- King of the Hill has Kahn and Minh Souphanousinphone, the Hills' Laotian-American neighbors. They speak in thick accents but their American-born daughter Connie does not.