The United States could break up quite fast given the right conditions. People call me crazy, but the state I see as first to leave will be Alaska. The people there can break away much more easily than the rest.
That is, how come an anti-US coalition couldn't be formed in Mexico with the help of a Russian centric 'defense' force - similar in construction to NATO - that immediately turned around and signed a treaty with joint military presence comprised of, oh, how about Russian, Chinese & Iranian 'advisers'?
Oh, that's right, something about the Monroe Doctrine. Well, for the numbskulls pushing this strategy in E Europe, guess what? Russia will go to the mat protecting its sphere of influence.
But just because they (at the moment anyway) can't pull this game off in MX doesn't mean they can't roll up Poland, the Baltics, and even some weaker states like Turkey, Greece, etc.
The US/NATO has demonstrated over the last 20 years that it's pretty simple to help overthrow a government - even if you have to bomb them like Serbia. Afterward, all you do then is carve out a partition, recognize the (new) sovereign state/enclave, and and then bring forward the appropriate trade and military base agreements.
We had a great 23 year run while it lasted. The petro-dollar still strong, sufficient conventional fossil fuel resources here & abroad, (semi) cohesive national interest.
Now, all reversed - especially the part about cohesive culture and national interest.
I agree with you save for the identity of the state. My hunch is Hawaii will be the first to break away.