I don't know, I think the opening of the Civil War could be replayed quite accurately in the modern-day America. The opening shots of the Civil War weren't Lincoln's troops firing on civilians in a random Rebel town, it was Rebel troops firing on a Union fortification which refused to evacuate.

I think this is exactly what would happen in the modern day.

"Proper" referendums don't include shooting. Certainly, violence against a military installation will be met with overwhelming violence in return. That's why we'll hold a referendum: to avoid all that. If the soldiers want to hang out in their base that happens to be stuck in the middle of Lesser Midwesternia, that's cool. If they get bored and go home, that will be cool too.

I'm not sure if it's a question of how civilized people are, but I get the feeling that the key reason why a certain number of people do not want Gun Control in the US, is precisely because they want to have access to weapons and resist, should the Federal Government turn tyrannic one day.

Yeah I've heard this explanation as well. It calls to mind Schneier's admonition against "movie plot threats". The reason to have firearms is not to counter any specific threat. We arm ourselves, rather, in order to respond effectively to a wide variety of potential situations. Among those, the "rogue federal government" threat isn't more than a rounding error, in the USA, for the foreseeable future.