I mean one could argue that Tibet is an invaded country, but that’s besides the point. The only way we would realistically intervene is if China decides to either invade an American ally like Taiwan, Japan, or South Korea or if they directly attack and declare war on the US proper. Even then, it would be quite a stretch for us to have soldiers reach western China, but if we did and if our soldiers found camps where people are imprisoned, then we would have a similar reaction to what we saw towards the end of WWII. However, until then, we don’t have sufficient grounds to invade a major world power.