Your framing just leaves something to be desired.
(WARNING: LONG RANTY POST ON A COMPLICATED SUBJECT I'M NO EXPERT IN AHEAD, FEEL FREE TO IGNORE)
"This game doesn't have a character representing this significant chunk of the world." Okay, sure, but population figures aren't the one lens through which to look at representation and diversity. It's about capturing particularity, enriching perspective, subverting a marginalizing default. "But the cast has no one from China, the most populous country" is a valid line of criticism, yes, but also...incredibly reductive, and a poor basis from which to dismiss such a promising cast.
Like, think about it this way. Black women make up 1/4 of the starting characters. For so many reasons, the fact that there are far more, say, Han Chinese in the world than there are black women doesn't at all mitigate how great that is. That just isn't how this works. At all.
Add in the whole American Diversity concept you've introduced to the discussion, and it feels like you're being a touch shitty. Diversity is diversity. And diversity isn't just some scientific attempt to reflect population figures, but also something that interacts with historical, cultural, and societal forces. When you invoke that American Diversity thing, you're doing two things at the same time: pretending that diversity works best when it's blind to specificity of experience, and weirdly enough, dismissing as "American" even the representation of populations who live mostly outside the United States. (By the way, for what it's worth, Indian and Chinese people are a hugely important part of the American fabric...)
Now, I think you're totally right to ask for Apex Legends to do better, and the absence of characters that represent the groups you've talked about is definitely a blindspot that warrants discussion. But it's a pretty damn good starting cast of 8 characters, and for all the room for improvement that exists, that reflects less a failure of diversity than things like cast size limitations.