Nonetheless, it isn't going to reach the point of the government dropping atom bombs on their own country. The US has forests, cities, and mountains; good partisan country. Heavy weapons aren't effective in these terrains. Even the actual Nazis were held at bay for weeks and months by armed urban uprisings.

The more realistic scenarios don't actually involve the military itself turning against the people. It's far more likely that police will overstep their bounds a little and try to go house to house, and one reason they don't do that, outside of exceptional circumstances that the public will back them up on, is the fact that doing so is actively dangerous.