We've run this experiment several times and gotten the same result every time. Hence the forever wars. Hillbillies with guns and IDEs have shown to be pretty effective against militaries.
By being willing to take significantly more casualties, usually because the fighters are ideologically motivated. If you want to be a martyr, keep your guns. How much do you want to bet you'll still be around to see that bright future you take up arms for? Or that once you win, the leaders of your rebellion won't toss you out onto the streets? If you want to stay alive, being a refugee is a much better bet.
Even if you are right, that would imply that the US would enter a protacted civil war that would impoverish everyone. I have a feeling popular support would swing away from the millitias very quickly, just how long do you think millenials will survive without their avocados, yoga classes and fair trade locally brewed artisanal beer.
I'm not sure why you started with this. Your odds are way better if it's against your own military, especially in the West. There's going to be a ton of defectors. Have you met anyone from the South? Those same people who are extremely anti government are usually vets. This isn't just speculation either, there's very clear examples.
But something people constantly forget is that you can't rule the dead. People are a resource. You need them to produce your economy, make your food, tax, etc. But there's also an argument here on the converse side, to make your people rich to make your ruling class even richer. But short term thinking...
Just take a look at what is happening in Virginia right now - police and veterans are siding with the militias in opposition to the incoming gun laws. I have a hard time believing that the men and women of the military would side with the government when the orders are to kill your neighbours.
Maybe in a failed state like California or New York, but that's not the entirety of America.