Michigan would go down faster than a $20 whore, especially when compared to the Santa Cruz Mts. The terrain is extremely difficult, and populated with very accurate shooters (trust me.)
Firstly, give me a break. Secondly, it's a moot point as the blue states with their larger pop centers/cities would be hit hardest by the leading nuclear strike. Huge losses of population and resources. Leaving remnant populations and potential insurgent fighters to migrate into more rural and intact red states. maybe. Regardless, some southern boys holed up taking pot shots at the enemy won't get the job done. I'd imagine that isn't how they'd fight, they'd organize into heavily armed, mobile forces and hit the swamps and deep forests and mountain ranges. It'd be hell facing them, along with all the other scattered insurgent forces. I wouldn't want anything to do with it. That's why we'd get nuked into oblivion, and our aggressor would get nuked into oblivion, first. Sadly.