As we learned from the American Civil War, the southern states were incapable of seceding. However this isn't the question at hand. The above user asked this:
The outcome of a war 160 years ago has utterly no relation to how a decision to secede would play out today. I use the word "process" in place of "whatever sequence of actions" might occur if states were to assert their intent to separate from the country. "Secession" might not even be an appropriate term - a resolution could be introduced, through all the correct and proper channels, for the United States to dissolve in an organized fashion, as the Soviet Union did in 1991. There's really no point saying any political proposal "can't" happen.
My point is the North employed violence in the form of a successful military campaign to maintain the Union. Where the North failed was following up with a re-education campaign to squash southern propaganda, such as the myth of the Lost Cause.
Tell me you don't live here (or know someone who does) without directly saying it
I've seen mounted MGs in the mountains, my guy, you don't know what's actually here and in the hands of some CRAZY leftists. I know 2 different people who have offered me very illegal arms should shit ever hit the fan, one of them owns a functional truck they just need to slide a tripod into the back into some homemade brackets and they can have a mounted MG truck in like 10m
Fuck, I've seen an actual RPG get shot (that was wild)
Without industrializing the North could have lost the war to the South as they would have been more evenly matched. The North needed to win the political battle, the war, and then after the war, the culture war. They won the first two, but we are still fighting the culture war.