There are an estimated 100,000,000 armed U.S. citizens, who possess an estimated 300,000,000 firearms. Millions of them are also hunters, which in wartime we call snipers or marksmen.
Even if only one in ten of those Americans chose to stand and face an armed aggressor (foreign or domestic), they'd still number 10,000,000 strong. That's almost ten times the size of the combined armed military personnel of the United States.
During the Iraq war, it's believed that there were never more than fifteen thousand 'insurgents' in country, but they held our entire military at bay for nearly ten years, despite the fact that they were heavily out-gunned by a technologically superior force.
Now I ask you. What do you think would happen if those same forces attempted to subjugate tens of millions of armed Americans through military force? People who are standing and fighting on the soil of their families and forefathers?
I'll tell you what would happen. They'd be crushed.
Factor in the number of desertions, defections, and refusals to fire on their own countrymen by members of the armed forces, and the picture grows even darker for any such misadventure.