I just don’t see civil war happening. General chaos and the worst kind of anarchy? Certainly – but a well organized, goal-directed civil war capable of “retaking” the constitutional republic that once was? I just don’t see it within the realm of reasonable possibility.
Just maybe, general chaos and the worst kind of anarchy would allow dedicated groups to create their own socioeconomic and political environments without what we think of a civil war. General mayhem will diminish after a while due to the lowered population levels. Anyway as long as we have the current governmental and economic structure things will be as they are.