You were slackin at your job if you don't understand that the majority of people would oppose these insurgents, by definition, since that is how democracy works.

There is no situation in which domestic insurgents would not be crushed utterly. They'd be heavily restricted in movement, denied resupply, theyd lose contact with their families, friends, etc as well as all cellular communication. They would not have air superiority. They wouldn't even be able to contest air superiority. The most advanced counter-terrorism force in human history would be tracking them. When caught, they will absolutely land in Gitmo, at best, and will absolutely give up everything because these are not hardened fighters, these are your neighbors.

The US is a fucking fortress. This is a complete non-starter. We haven't even touched on actual military engagement yet. I'm not convinced it would even ever get to a point where it was necessary.

If it ever was, the US would have to show the world that a challenge to its supremacy on its territory by (now non-)citizens in open rebellion absolutely will not be allowed to happen.

The affected areas will completely locked down. The insurgents will lose all access to travel, because the entire area will. Then it's just counter-terrorist procedure practiced over 20 years thousands of miles away.