I don’t feel well educated in modern military actions- are you saying that civilian gun owners in America would contribute meaningfully to the national defense (maybe because of things like civil resistance in other modern conflicts?), or am I misunderstanding? Do you have any suggestions for how I could start to broach the topic? It’s so broad and fast-moving that it’s hard to know where to start.
Yes absolutely they would and insurgencies are not the same thing as two nations fighting each other. America has twice as many gun owners as there are people in Afghanistan, a large chunk of them have combat experience.
What makes you think the us army would unite against them? Sure a few nut militials would be suppressed, but if gun owners in mass are raising up that means a large controversy that the military will be aware of. The us military is not full of 'yes men' who will follow orders that blindly on home turf, a lot of them will follow.
i doubt we will see this in my lifetime
The thing that makes the large quantity of American gun owners potentially useful in that sort of scenario is not that they possess guns. That matters a little, but usually most of the equipment a resistance uses is captured and/or supplied by allies. The thing that would be useful is these individuals' skills with firearms. It's theoretically kind of an alternate route to a similar (but lower) background proficiency level that some countries achieve with mandatory military service.
Note however that America is not only not unique in having that background proficiency -- but unlike mandatory military service, this approach has not really been tested. It's far from a certain proposition either way.