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...
Maybe in a failed state like California or New York, but that's not the entirety of America.