The only serious racial question in America is the black question, and black nationalism is going to have a hard time fighting a civil war. Most black people want desperately to assimilate into white America, and the race question itself was always necessarily tied to the economic system of slavery and prison labor.
The Mexicans and Latin Americans in general are, if they're rich enough, basically honorary white people, and there's never really been a serious race question. Again, the current situation is almost entirely about the economic system and the need to maintain illegal labor.
In the Balkans, you're talking about groups that literally never saw each other as the same thing, or even close to the same thing. A Serb was a Serb, a Croat was a Croat, and that was that. They were ruled over by another foreign empire that had nothing to do with them, which had a hell of a time dealing with the separate groups. You don't see anything like that in the American states, not even the Confederacy was like that (because the South was fighting for a primarily economic reason, and they had before the Civil War agreed to join this thing, the United States, as an equal partner given some comfy concessions).
Racial narratives is one of those narratives that gets played a lot and built into more than what it is, especially in the modern era. Neo-confederates desperately need to believe for their own pride that the blacks really are inferior by the rule of God and that whiteness is something special and mystical, and liberals sold out to eugenics and race-science a long time ago though they're too polite and have the sense now not to advertise those beliefs too hard. It makes sense that they want to utilize every racial and social divide possible to segregate people, because their mythology depends on in-groups and out-groups. But it really is about institutions and people, political power and class. That has always been the overriding case in America, even if Americans themselves obscure it in mythology and are blinded by their class and social system.
As for conservatives and Democrats fighting each other, that's pretty laughable when the shit hits the fan. Most of the country hates even talking about politics, but if they have political inclinations, normie conservatives and normie liberals basically don't want to fight each other, and certainly won't fight over the stupid wedge issues they are presented with today. No one's going to fight a civil war over abortion or gay marriage. Some wingnuts might take up the cause of killing liberals (I doubt many liberals are invested in killing conservatives), but such people probably aren't even reliable enough to elevate as temporary thugs.
The most likely case for American "civil war" is that the police state bloats and begins devouring the country completely, until it is left a husk. What happens after (if there is an after) is anyone's guess.
Honestly though, in the long run, if Asia takes over as the center of global political and economic power, it is very likely that its culture and system(s) just perpetuate throughout the rest of the world, and America becomes just another vassal. Maybe an important vassal, because North America's geographic position and political makeup would still make it pretty big, but as I said, global Empire today doesn't really benefit from splitting up occupied territories. The current policy of globalization relies heavily on regionalization and integrating large parts of the world together into manageable units, rather than drawing new arbitrary boundaries, which is inevitable given both capitalism's tendencies and the practical realities of technology favoring centralized states and regions.