The United States is completely aware of the atrocities being committed and no amount of additional war crimes will change its position.
Its interests in the region that it views as necessary to maintaining its global hegemonic power are viewed as more important than any action by an allied actor even to the extent of what a decently large portion of its populace deems genocide.
China is subsidizing the transition away from fossil fuels which greatly accelerate climate change and if not taken seriously immediately will lead to the deaths of tens of not hundreds of millions in the next few decades. The speed at which this transition occurs is vital in saving human lives and preventing infrastructure losses previously unfathomable. Their actions towards green energy adoption both domestically and abroad are one of the few things that provide any sense of hope about a better renewable future.
On the other hand: BUT AT WHAT COST