You're getting into spherical cow[1] territory if you think the US citizenry couldn't defeat the US military.
The US military will not be fighting the US citizenry in a hypothetical clean room, it'll be fighting in America. Who are you going to bomb, who are you going to strafe, when your opposition can quietly fade into the populace that provides your material?
I'm tired of reminding HNers about Aghanistan.
Who has the better chance at ambushing and getting away with the enemys weapons: the one with the gun or the one without a gun?
Look at Turkey. The primary tool was encrypted communications and information dissemination. That’s modern power that citizens should have. Right now power comes from information and the preservation of speech and private communications, not a few handguns and rifles (or IEDs).
When the 2nd amendment was written a gun was relatively way more powerful than it is in today’s world. If you had a group of men with guns you were basically on par with the government military.
However, I'm not saying I'd want them a civil war, just that it failed despite doing everything "right" it seems.
Unless the US were to nuke itself, given the geography, a motivated citizenry could easily take on the US military. Not a scenario I want to imagine, but the US military has troubles in Afghanistan and Iraq — imagine that kind of conflict in the US. Just look at rebels in Syria to see this on a smaller scale.
The guns that a person are allowed to bear are nowhere near sufficient to take on the US military, and the modern arms such as encryption and freedom from surveillance are not even guaranteed by the 2nd amendment.