I don't see why we should draw the line there. Star Trek tells us 600 million people are going to die in a WW3. You think that is consistent with a positive future, but if the majority of those 600 million were Chinese it's not?
I don't think Star Trek is telling us the Chinese were (largely) "wiped out", much less that there's been a "genocide". I'm just trying to make sense of the dearth of Chinese people -- or really, Asian people in general -- in the future of Star Trek, which doesn't make a lot of sense when it's the most populous part of the world today.
I can think of two explanations:
- Asia's share of the world population remains more or less the same, but for some reason Asian people don't serve as much in Starfleet. This, to me, would be the more problematic explanation, because it suggests there's still racism in the 23rd and 24th centuries.
- Asian people are just as likely to serve in Starfleet, but Asia's share of the world population has declined. The obvious explanation for that would be World War 3, especially since we're told an Eastern Coalition fought in the war.
Since large cities in East and South Asia are both more populous and more dense than North America's, even a tit-for-tat nuclear exchange would lead to far more fatalities in the former than in the latter.
Consider: only two metro regions in the US have a population of
more than 10 million: New York-New Jersey and Los Angeles.
China has eight metro regions with 10+ million inhabitants.
India has five.
Pakistan has two. The Ho Chi Minh metro area has a population of 20 million. The Jakarta metro area has 30 million. Taipei 7 million.