The only sport I can think of with more international athletes in the US is hockey. There are tons of fighters from all over Europe (Croatia, Armenia, Netherlands, UK, France, Germany), Asia (Japan, Korea, Russia), Brazil and even Africa. I think you don't see more Chinese fighters for a couple of reasons, first it's very much a closed society still, second it's much more difficult to get permission for Chinese athletes to live abroad, and third and probably most importantly MMA as we know it is not that big of a sport over there. In a country of a billion people you would expect to have some seepage, but then again how many Indian (dot not feather) fighters do you see in MMA? Not many, again they have their own sports and MMA probably isn't really culturally relevant to some countries.