As for the US/China alliance... Where were the Chinese? Yeah you saw them in the background but that's about it. You didn't even see them anywhere as part of the alliance forces. Interesting if there was something the series never got a chance to show. Realistically that alliance would never happen. More like divided by US and Chinese spheres of influence but they would never tread in that direction. Besides I read in an interview that Joss Whedon originally had it with the Japanese but his wife was more in tune with world affairs and told him to make it Chinese.
For those unfamiliar with the series, in the firefly sci-fi universe, the bulk of Chinese space immigration went to a planet named Sihnon, which is also the home to Inara Serra.
When mankind first colonized space, Earth was still divided between the American and Chinese sphere. The Americans went on to establish the colony planet of Londinium, while the Chinese established Sihnon. These 2 planets became the major power houses, while other colonies were small and mostly rural. There was no strong central authority that extended out to the colonies.
Sometime after, the governments of Sihnon and Londinium decided that they'd join forces and bring the entire human civilization across space under one central authority, the Union of Allied Planets (aka Anglo-Sino alliance). The border planets refused to submit and eventually lead to the unification war, in which the rebels lost. The TV series takes place a few years after that point.
Some folks complained about the lack of Chinese people in the TV series. Had the producers been given more money to complete the TV series, they might've done an episode set on Sihnon or some other Chinese colony and actually hire a bunch of Asians for the shoot. But the funding was cut short and the series ended prematurely. =/ If only they had been funded by the Sci-Fi channel.
Racial/ethnic presence and relations in TV shows has always been a pretty hot topic. I think Firefly should have hire more Asian actors, but not done in an overly-PC way like... ultra-feminism in ST: Voyager, or the black/white interracial pairings in the latest Doctor Who TV series. Geez okay we got it... you want to show modern UK is not racist, fine, but the sheer number of black/white couplings in the show + Xmas special is just silly.