Were a seccession moment come, it's unlikely that all those red counties would continue to be happy to be ruled by the massive blue metropolisis at their centers.
I foresee both ethnic and political cleansing on a large scale. Archy has suggested the model for an American CWII event is something more like 'the dirty wars' of Argentina and Chille in the 1970 and 80s, and less like a CW1. I think he's probably right about this.
Most of the examples of peaceful succession cited are countries with relatively small populations at the time of succession. The most notable exception was the Soviet Union.
Our nation is huge and we of course have already had a bloody civil war. Any succession movement would likely be triggered by a hard tyrannical act by the Federal government such as martial law.
If all (an I mean all)our peaceful efforts fail, tyranny will harden in place over time. The only way to destroy it is through a relatively peaceful coup (as with the Soviet Union in 1991) or a bloody civil war/ second revolution.
That is, to the best of my understanding, what happened in this country in the aftermath of the Rev War.
Loyalists either sat down and shut up (if they hadn't pissed-off the neighbors too badly), or moved to Canada/England.