The problem is that the Red/Blue divide is not so clean. The Constitution recognizes States, and the Electoral College tallies by State vote, but the breakdown is at a much lower level. Many "Blue Staters" live in Red States, and vice versa. A map showing the 3000 or so US Counties makes this plain:
The mapping shows a mostly rural vs. urban divide, although there are some clear exceptions to this - the Indian Reservations in New Mexico, for example, or the southern border of Texas are strongly Blue. The Mississippi river runs Blue for most of its length.
And so when we consider the possibility of secession, things are very messy for the States. Much of Georgia might be eager to secede, but would Atlanta? Probably not. There would be considerable unrest in any State that seceded, and likely much unrest in many of those that didn't.
That actually is pretty much what happened in 1861. There were many in the South who did not want to leave the Union - Robert E. Lee was one; Virginia was late to join the Confederacy, and until it did, the Union Army courted him to be its commander.
There are regional grumblings about Counties seceding from the States: several northern California counties have voted to create the State of Jefferson; upstate New York has long been a hotbed of secession talk, with several communities looking to join Pennsylvania; the Pacific northwest has groups proposing the nation of Cascadia which would include some of British Columbia (it even has a redit group!).
We should also remember that both Vermont and West Virginia are the result of secession (from Virginia and New York, respectively).
And so secession isn't really a State issue. It's regional, just like in Europe (Scotland, Catalonia, and northern Italy all have active secession/devolution movements).
Given the fragmentation that would be the necessary result of a secession movement, we can expect the prospect of chaos to act as a break on any action until there is overwhelming support. Right now the political elites are happy with the current situation - the GOP establishment is content to take the bribes and rake offs that the Democrats enjoy, and so don't rock the vote.
It will take a crisis, and external shock to change this - an financial crisis. I expect that there's one coming:
I think that this road that we are on leads to secession. We've already seen a geographical divergence of governance, with Blue states increasingly pushing the Salad Bowl grievance identity politics (limited growth with government distributing the jobs) and with Red states pushing pro-business, pro-growth politics (i.e. melting pot with enough jobs to go around). This will not continue forever: a middle class increasingly under financial pressure will flee the Blue states, increasing the fiscal strain that those governance models experience. At some point the Blue states will demand to be bailed out en masse, and the Red states will refuse.California is the place to watch, with a public pension crisis of epic proportions boiling right now. Already cities are going bankrupt, and the State is (like the EU and the Eurozone) frantically trying to paper over the mess. But since no actual reform is taking place, the old adage is true: what can't go on forever, won't.
At this point the split will occur. I expect it will happen within my lifetime.
At the risk of speaking for my fellow Georgians, I can't see support in the Peach State for bailing out a bunch of Blue State governments who spent way more than they should have. Even Atlanta will likely not be enthusiastic (and note that Atlanta has its own secession movement in north Fulton County, so the part supportive of a bailout is likely going to shrink over time).
It's possible that the bailout will be done by stealth, with deficits funding the program. The problem is that the dollar is in a crisis, and when financial corrections come, history shows that they come suddenly. The crisis in this scenario will be no different, other than much bigger.
I see one likely path to a split: a crisis causes local and regional political elites to seize on the public disgruntlement. As with all elites, they are part of the problem, but the crisis of confidence in the current national governance will give them an opportunity to retake power from the center.
Really the only question is whether the crisis will be small (pension bailout) or large (crisis of the dollar). Fewer States will secede in a small crisis; a large crisis will likely leave nothing standing as the Blue regions decide that this is their chance to go full throttle Euro-Welfare-State.
I expect there will be a lot of migration after the breakup. We see lots of people moving south from Blue States to the better climate and economic opportunity of the southern Red States. Californians are leaving for Texas today. This will be a lot bigger after the breakup, as Blue regions get bluer and Red ones get redder.
Tomorrow will discuss the International Implications of secession.