For "bigger guns", read control of media, communications, finance and surveillance. Just look at what happened to the Canadian truckers. Americans may be heavily armed, but they are not an organised force. Without something like "V for Vendetta" levels of organisation, it’s hard to see how fragmented civilian armies could mount any serious challenge to the state. Nor can I see the military defecting unless the government had already entirely lost legitimacy and control.
And do most people even want freedom? With freedom comes responsibility and all that. In Ireland, 60% of the population receives some sort of government handout. Are they going to bite the hand that feeds unless that hand can no longer do so? I suspect you have rather more faith in your fellow man than I do.