This is silly, guns can't protect the population against the modern government. It would start by running a disinformation campaign to turn citizens against each other, then would purge large swaths of the resisting power structure using slaughterbot-type approaches. Areas of significant political resistance would be wiped out using chemical weapons, or even nuclear weapons. The weapons of the U.S. Military turned against the population of the U.S. would be efficiently horrific at reducing resistance. Oh, you think the U.S. Military wouldn't do that? Nazi Germany is calling and they want their history lesson back.