If you take it that far, minority representation in media is just a microcosm of the general racial issues in the US.
That's always been the case.
As for British TV is has it's own problems, granted I still think they're ahead of the US (not hard to imagine). Black men struggle to get roles; but on the flip side in an interview with Idris, many of the writers write their protagonist without much care for their ethnicity; before Idris Luther was suppose to be white then Neil Cross saw Idris Elba's acting and was determined that Idris be John Luther. I know on the show Utopia, Nathan Jarrett's character was suppose to be white and they simply made him the character and didn't change anything about said character to reflect the fact he's black.
On one hand I think that's better than our current status quo in the US where writers make sure to let viewers know "hey this is a black character! You can tell by how he stereotypical we made him!" and can reflect the fact that black people come from all walks of life and not just the assumptions that the media at large believe (we're all poor, ghetto, speak ebonics, etc); that we too can have the same upbringing as any other group of people.
My problem with black representation in video games is that we're always gang members, angry gun trottin thugs or basketball player. And in that sense I call bullshit on someone's inability to write a better black character because "that's all they know". You don't need to be black or even have interactions with black people to write a character who doesn't fall into such ridiculous 'archetypes'.
I'm willing to be the person who wrote Adwele wasn't black and probably didn't know many if any black people; yet he was able to craft a good character. Same with the person who wrote Aveline's character. And I also refuse to entertain any argument that these guys are simply some outlier/rare writers or any such shenanigans.
I don't know much about Native Americans, but I can sure as hell bet you that if you give me an encyclopedia/Wikipedia I can write a character that isn't some stereotypical Native American caricature who wears a headdress (despite not being the leader of a tribe) and drinks booze while talking to spirits. Again ignorance isn't an excuse in my opinion especially when something can be researched; point in case Connor from AC3. Ubisoft went and researched about local American tribes despite being a French team and not having any Native American writers/developers on staff.
TLDR - I think the argue of people simply writing what they know is a major cop out. That absolutely flies in the face of all the information we have available at our fingertips; you can basically know anything you want to because of the internet. All we're seeing is laziness.