Sure, if the civilian population of the US had to actively repel an invading army with their own organized militia, it’d be completely one-sided.
But if the US military were engaged in a war against its own civilian population, it wouldn’t be a remotely straightforward fight. They’d be dealing with a local population and the emotional impact of fighting their own population at the same time. Guerilla warfare in the United States would be a mess to try to deal with. We have a lot of wilderness, and the division within the military would likely be significant enough to have a major impact on any attempted operations.
The US military is really good at organizing its troops to fight for the US. Fighting against the US is a whole other can of worms. And by my count, most older vets wouldn’t be on the side of using the military against our own civilians, whether they’re otherwise more on the conservative side of politics or not.
I don’t think there’s anything like the kind of support or organization to see something like that happen, but I think it could get a whole lot uglier and more complicated than just the numbers suggest.