Well, sadly, it's of course violence. The basic contract of government is you give up some liberty for safety (Hobbes), i.e. you don't go around robbing people, and the government will see that no one else goes around robbing you. But this sort of first form of government was inflexible, and if you wanted to change it you basically had to kill the people in charge. The chief innovation of liberal government was "self governance", and the trade there was "OK, we'll listen to you, you don't have to murder us to effect change". Practically everyone does this via some form of voting.
But as soon as that contract breaks down, i.e. the government stops listening to you, then that contract is breached and generally trouble starts. It gets (arguably) even worse if the government falls entirely, because then you get the kind of lawless marauding you had before any government.
I mean, I guess the argument here is "well, if the gov't goes crazy we still have weapons because 2A let us amass them". But in reality, the US government is unimaginably powerful. Like they could easily take control of all energy producing facilities everywhere, every major city, port, road, railroad, airport, hospital, etc. There are probably close to a million law enforcement officials in the US. And all that's to say nothing of advanced military, surveillance, and espionage capability.
Basically, the idea that 2A would let us protect any semblance of our current way if life is fantasy. The most you could hope for is to join a resistance and dig in for a generations long, probably species destroying authoritarian regime to run its course.
But as soon as that contract breaks down, i.e. the government stops listening to you, then that contract is breached and generally trouble starts. It gets (arguably) even worse if the government falls entirely, because then you get the kind of lawless marauding you had before any government.