The cause of a race war is tribalistic factions battling for cultural/political/financial domination.

I feel it’s hard to speculate exactly how it would go down, but I can say for certain the end result would be a fractured nation of independent bodies whose purposes would be to protect their respective values from the “other”.

My biggest fear would be the weakened position the US would sit in. China and Russia would be free to do whatever they want should the US devolve to tribal factions.