Doesn't that presume an intact military fighting for the government?

[Lizzie Poppet]

That's not an assumption I'd be willing to automatically make. If some sort of civil war erupted, based on certain political/governmental actions, the sides would likely fall out based largely on socio-political views. The modern US military has a fairly pronounced rightward tilt (and its officer corps even more so), so if the "loyalist" side was under a left-leaning government, I think you could pretty much bank on a significant portion of those forces defecting to the opposition.

Among other ramifications of that scenario is that complex weapons and communications systems (the primary advantage of regular military forces over insurrectionists) would suffer from that fragmentation of the military. It requires intact, functional logistics systems to keep them operational, and with probably a bit more than half of your personnel defecting (if not engaging in outright sabotage), those logistics systems will be in shambles.

Any real scenario of widespread insurrection would see reasonably well-matched forces. And would be an absolute fucking nightmare for us all...