On one hand we all know race does not dictate personality, we have plenty of nerdy blacks and "Soul brother" type whites. Most, but not necessarily all blacks who exhibit "White" personality traits grew up surrounded by similar whites. Likewise we have plenty of thuggish whites because they grew up around stereotypical thuggish blacks and whites in ghetto neighborhoods. As well as blacks and whites emerging from their designated communities who don't act "Properly" because their personality just so happened to be unique. In this case Art Imitates Life. So portraying your token black(s) among a white cast that isn't 7 feet tall and beastly muscular relative to the biggest white man, unnecessarily violent, starting problems, screaming every time the black man looks at a white girl, and can go at least five seconds without saying "Nigga please" is ideal in modern media. Showing the audience that both groups are alike.
On the other hand, using this trope while also lacking black characters possessing positive and truthful "Black" traits shows a complete lack of awareness regarding different groups and cultures. While the trope's implications are noble, it is rarely used to show different races of characters in a positive light; But instead because the writers lack the ability to write a culturally appropriate colored character, or they can and decide to portray the "Whitewashed" black as evil because he has "Betrayed his people" or a victim because he was "Brainwashed" by "Colonial whites". When in reality he just adopted his personality due to being raised differently.
This trope is more common in American children's media due to its diverse racial history and makeup, with most non-whites making up for double digit percentages; Where other countries have significantly lower minority populations, therefore the assumption by those who never met these minorities, albeit also prevalent in America, is that the minority population is different than them, and could never fit in.
