“Does anybody see a way out of this? What would such a conflict look like with no clear geographical or physical boundaries between the parties?”
I think it looks like Bosnia.
My own view is that people moving in the USA to either join, or get away from, coastal woke liberalism in a geographic self-sorting that make a future division and partition of the USA all the more likely.
I think something similar is happening here in Canada, although high house prices in the high-cost liberal enclaves is a big factor.
I think that Brexit represents the same thing - an attempt for ordinary people to escape from urban, progressive, woke, liberal, globalist tyranny.
Never underestimate us Hillbillies from Pennsyltucky.
The only way to avoid a long and bloody civil war is for President Trump to go full Pinochet. With the backing of the military, dissolve Congress. Then give free helicopter rides to about 50,000 communists.
The alternative is several million dead.
I think people who have never planned for it desperately wish it would only look like Bosnia.
I honestly find it more likely to look like the civil war in the Marshals, where every building as large as a porta potty was burned to the ground.