If the supposed evil guv'ment takes over, they're doing it on their home-tuff and time is on their side, unlike in Iraq or Afghanistan.
While it would be quite unlike Iraq or Afghanistan, I believe you are making the wrong assumption about the "ebil guvmint" having time. Unlike the rest of the world, we, as a people have held the idea for a long time that govt serves at our pleasure. We expect elections, and all our constitutionally guaranteed rights.
Any "evil guv'mint" actually oppressing our liberties by force of arms is going to be on borrowed time. The longer it goes on, the more resistance there will be. IN all kinds of ways, not just resitance by force.
While clearly, the same military tactics (overwhelming firepower, tanks, jets, etc.) will work in combat, doing that, particularly on a prolonged basis, and over a wide area in the US will NOT go the same way it does in third world pestholes.
Muslim terrorists have a very, very, very narrow window of sympathy in our military. Hundreds of thousands of troops, and you maybe find one, or two willing to give information to the "rebels" or toss a grenade into a tent.
Active combat ops, against the general US population? Don't make me laugh. Our troops are OUR SONS AND DAUGHTERS! While you will have a certain number of people willing to just follow ANY order, until you create special units made only of people like that, your combat efficiency is going to be waaayy down. And, when you DO make units of "loyal" troops, you are going to find them to be the "enemy" to not just the US population, but a significant portion of the rest of the military.
No, FA arms in civilian hands don't equalize against tanks and airpower, but tanks and airpower can only destroy things, not control or administer. That can only be done by individuals on the ground. And that is where the "evil guvmint" will fail, ultimately.
Why deny us something that is both a constituional right, and in your view irrelevant anyway? IF civilian ownership of FA arms won't save us from the "evil guvmint" why would that same guv'mint be worried about it?
I think your argument is flawed, you haven't thought things through enough.