Being of a certain ethnicity doesn't necessarily mean someone speaks a certain language or even knows much of their heritage. Just because someone is of Mexican descent and their parents speak Spanish doesn't mean they will also be fluent in Spanish. Nor do they necessarily know much about their food or other aspects of the culture.
There is Truth in Television in this. For example, studies show that each generation living in a certain country are less likely to be bilingual than the preceding one. So a person who moved from South Korea to Canada will often have grandchildren who can't speak a lick of Korean. People who do not speak the language associated with their heritage can be made to feel embarrassed or awkward for it, or might have internalized feelings of inadequacy due to their lack of understanding, which may opt them to learn it as a second language later in life.
Compare to My Species Doth Protest Too Much, The Whitest Black Guy, Raised Catholic, and Trans Nature. They may try to connect with their heritage further by taking a "Rediscovering Roots" Trip, though doing so could result in Stranger in a Familiar Land.
- A Spanish language Goya commercial has a young Latina girl telling her mother that she has to make a cultural food for school. Her choice? Nachos. Her family is horrified and they end up making flan instead.
- One episode of Chihayafuru has the characters going against a group of "foreigners". They begin speaking in Gratuitous English with Japanese accents and mispronounce their words. This however was intentional. The characters were raised in Japan and can barely speak English. They were pretending to be from another country to freak out the competition.
- Massugu ni Ikou: Hanako didn't know she was a Kishu until she overheard her vet mention it.
- Fifth grader Ana Coppola of Strawberry Marshmallow, whose family is originally from England, has lived in Japan for as long as she can remember. She and her family have integrated to such a degree that Ana has next to no English skill whatsoever and is generally more knowledgeable about Japanese culture than her Japanese peers. This bothers her enough that she tries to ramp up how foreign she is at school and works with her classmate Matsuri to re-learn her mother tongue.
- Similar to the Chihayafuru example above, Olivia in Asobi Asobase likes to pretend to be a Foreign Exchange Student and speaks Japanese with a fake accent, but is actually the daughter of an immigrant family who grew up in Japan and can't even speak English.
- Langa Hasegawa from Sk8 the Infinity is half-Japanese and half-Canadian, but he's lived in Canada for most of his life and he and his mother moved to Okinawa after his father died, so he's out of touch with Japanese culture as a result. While he's mostly fluent in Japanese, he can't speak with Keigo very well.
- Diary of a Tokyo Teen is an autobiographical comic book about a teenager's visit to Japan. She was born in Japan but moved to America at a young age. She's visited Japan before but there's still a culture clash.
- Dick Grayson was retconned as Romani in the late 1990s. It's been shown that he doesn't know much about his heritage and doesn't understand the language.
- This is the initial conflict of Double Happiness. Tom, a Chinese-American from Brooklyn, moves in with some relatives in San Francisco's Chinatown. He doesn't recognize the culture, the food, or even the language his relatives are speaking. This leads him to fear that he's too white to be Chinese.
- In Heis'he Ri'nanovai, Morgaiah t'Thavrau has to explain an aspect of Romulan homeworld noble culture to her executive officer Sarsachen tr'Sauringar, who though also Romulan, grew up as a commoner on a border colony and spent fifteen years in Starfleet.
- Downplayed in the Jem fic Starlight Is For Always. Because of her Latin surname, it's thought that Pilar can understand Spanish, but despite her Mexican-American parentage, Pilar only understands English.
- Gold Eyes To Red: Alphonse is half-Ishvalan through his Disappeared Dad. He was raised by his mother and feels nothing towards Ishvalan culture. This gets him into arguments with Scar, who believes Al should learn about Ishvalans more. In the end, Alphonse decides to take up Scar's offer to educate him on Ishvalan culture.
- Kimi No Na Iowa: Inverted in that Imamura's traditionalism and insularity from the wider America means Ayaka is fully in touch with her roots; Japanese shipgirls are surprised by her cultural and linguistic abilities, joking about her secretly being one of theirs, and a friend of Nakahara's doesn't notice anything wrong when she uses a cover story of having come down from Gifu. Also discussed with both Japanese characters and older ex-Imamurans showing disdain towards yonsei and other subsequent-generation Japanese Americans who have lost their way.
- In Sweet Country, it's a recurring theme that the Aboriginal characters working for the white settlers are cut off from their ancestors' culture, many of them having been separated from their culture as children. When Sam and his wife flee into Aboriginal tribal lands, they're almost as out of place there as the white posse pursuing them.
- Half-Jewish on his father's side and half-Puerto Rican on his mother's side, J from I Am J was raised rather nonreligiously. His father rarely brought up his Jewish heritage or faith and only briefly tried to "act Jewish" when J was ten. As a result, J is pretty clueless on Jewish culture. He does remember one prayer, however.
- One of the side characters in Debt of Honor is Chester "Chet" Nomuri, a fourth-generation Japanese-American working as a CIA field officer in Japan. Several times, the narration of his parts of the story remarks on how different his ancestral homeland is from his birthplace.
- In The Big Bang Theory, Raj - despite being an Indian - hates the idea of living in India. The unexpectedness of this is played for comedy, especially since he is stereotypically Indian in other ways - being a geek, believing in Hinduism, etc. For instance, in one episode Sheldon's looking for mental challenges and Raj suggests learning Hindi, only to sheepishly admit he never learned Hindi when it turns out Sheldon already did.
- Duncan from Community often uses incorrect British terminology as part of a joke. He has lived in America from a young age and doesn't actually know much about British culture.
- Never Have I Ever:
Devi: Some old loser was telling me that I'm too Indian, and some other people think I'm not Indian enough.
- Played with, with Devi. She's the daughter of first-generation Indian immigrants, and though she grew up in the States, she still practices a lot of traditional customs. She's just not entirely good at them. As a corollary of where she grew up, she also behaves in distinctly "all-American" ways, causing her to clash with her mother and her relatives from Asia.
- Played with again with Kamala. Kamala is a lot more Indian "Indian" than Devi, having grown up in India. However, she's also not a traditionalist, and finds herself more inclined towards Western ideals as she lives abroad. Nalini says as much, saying she looks like "a careerist Western woman" when she attempts to meet her arranged-fiancé for the first time in smart jeans and a blazer which she is, Nalini concedes, but he doesn't need to know that yet.
- Daya from Orange Is the New Black gets scorn from other Latina inmates (even her own mother) for being Puerto Rican but being unable to speak Spanish.
- Ana Sofia from Telenovela is the lead of a popular Spanish-speaking telenovela but can't speak Spanish at all. Hilarity Ensues.
- Gentefied: Because of his family moving to Idaho when he was young, Chris is not considered "Mexican enough" by his family and co-workers when he moves back to LA.
- Estranged sisters Emma and Lyn from Vida are both Mexican-American. Lyn is mocked for not knowing Spanish fluently, while Emma made a point of learning it to grow fluent, since their family spoke only "Spanglish" before.
- In Dawn of a New Age: Oldport Blues, Daigo Hiraga is half-Japanese but white-passing. Combined with his tumultuous upbringing- his white father having abused his Japanese mother until she disappeared one day- he has some issues with his familial connections.
- In the intro fic to a Shadowrun Beginner's Box, the human character is surprised when the elf doesn't speak Sperethiel. Though, in that case it's because the language has only been around for a couple generations and was introduced by a group of separatists that her parents refused to join.
- Dragon Age: Inquisition:
- Sera is an elf, but actively (and, at times, violently) shuns everything "elfy" and is terrified of anything pertaining to ancient elven history. It is a consequence of her being raised mostly by humans, with little contact with members of her own race.
- A Qunari Inquisitor will also get this reaction from The Iron Bull if they speak to him about their heritage, Bull is quite insistent that the Inquisitor is not a Qunari since they were born outside the culture and don't follow the Qun, instead they are a Vashoth (as opposed to their parents, who are Tal Vashoth since they intentionally left). Given the way the Inquisitor reacts to certain phrases Bull uses it's implied they don't really speak Qunlat either.
- In Persona 2, party member Lisa Silverman has two white American parents who are naturalized Japanese citizens, so you'd expect her to be fluent in English, but she can only speak Japanese and Cantonese as a result of her Otaku parents wanting her to be a traditional Yamato Nadeshiko.
- Despite her blonde hair, blue eyes, and western name, the half-Scottish Lily from Katawa Shoujo is Japanese through-and-through. She can barely speak a lick of English and doesn't quite like Scotland.
- Little Busters!: This is a real source of angst for Kud. She's ethnically Russian (her full first name is Kudryavka), but she grew up on a fictional Pacific island officially owned by the USSR (a clip from the anime implies she was one of few white people living there) and then spent many years travelling around the world with her Japanese grandfather; as it was always intended that she attends high school in Japan, she was taught the language from a young age. However, when she does start living in Japan full time, she finds that almost all of her peers simply treat her as a Funny Foreigner type. She tries to fulfill their expectations, but due to her Japanese upbringing and terrible English skills she can't really manage it and ends up disappointing them. (Her Russian seems to be much better, but is also apparently less 'cute.') As a result she ends up feeling very isolated, and like there's no place in the world where she actually belongs.
- Sparrow from But I'm a Cat Person is Jewish by birth but, despite the attempts by her mother, is barely connected to her heritage.
- Numbuh 1 from Codename: Kids Next Door has an English accent but is American raised. When he and his father visit England, Nigel ends up confused due to the differences in language and culture.
- Penny from Littlest Pet Shop (2012) visits other pandas in China in one episode. However, she finds out she has little in common with them. In turn, they think America is essentially how it was in Singin' in the Rain and other older film musicals.
- Miraculous Ladybug: Marinette Dupain-Cheng has Chinese ancestry through her mother's side, but is terrible at speaking in Mandarin compared to blonde, green-eyed Adrien Agreste. Played for comedy rather than angst or drama when a relative of Marinette's from The Old Country comes to visit and Adrien is drafted in to translate while her mother is busy elsewhere, impeded by Marinette's inability to be near Adrien without turning into a blushing, stammering and all-round fangirlish mess.