Why would China go into such a giant quagmire that would most likely lead to nuclear exchange?
Chinese expats who willingly chose to aid the enemy at worst and at best only have coincidental ethnic ties to China are alone not justification for war. It'd be like America going to war over south African whites, except worse because South Africa doesn't have nukes and is much less populated.
In fact China should not bother with mainland USA and only focus on sea control. China only needs to enforce a favorable free trade agreement with the new USG, anything else they do is fine. Let them have their based trad right wing gilead dictatorship, that means they'll have no power outside of north America. China should even encourage such a development.
Having control of the Pacific, south America and the world island, China can let America have their playground in north America, in that way, there's no threat of nuclear tension. They can go ahead and act like animals there, kill as many blacks, jewish, Asians etc. Although most Chinese will probably just move out. Their government will be confronted with the stark reality of needing Chinese goods to survive and the threat of surrounding PLA garrisons, hence their market will remain open to China for profit extraction. As I see it, it's the safest approach to managing America.