See, this makes massive, massive assumptions about the majority of the populace that I just don't think are true, and also seems to make rather massive assumptions about how widespread support for the rebels would be, how big a warhead we are talking, what gets hits, and also about the ability of any rebels to get to the point nukes are needed to break them instead of glowies or normal LEOs.Umm… pretty sure it’d be suicidally dumb of the Feds to nuke their own soil, friend.
Maybe you’d get a few crazed general officers and seething ideologues who want to, but ultimately, the costs of nuking your own country, your own infrastructure, and millions of your own citizens outweighs the benefits exponentially. In addition to how tons of economic assets are gone if you do that (farms, factories, power stations, and so on), your remaining citizens will run screaming into the open arms of the other side, while other nuclear powers watching from the sidelines threaten to fire their arsenals off at you lest they be next. Sure, I guess it’s theoretically possible the DC elites could become that desperate, but whatever victory they score will be the most pyrrhic in history at best — not the trump card you seem to believe it’d be.
I think you are rather naive about how a lot of the populace views nukes as related to civil war situations.
I doubt we will ever get to the point we find out, though, because frankly I doubt another civil war is coming, and frankly think WW3 is far more likely than a US civil war these days.