"which is safe enough because rural populations are very sparse and small arms are really only dangerous with large numbers behind them"
Last year there where 750,000 hunters in the state of PA alone. They constituted the 7th or 8th largest body of armed men in the world. If I remember correctly Wisconsin came in second with 650,000. My own state of WV had around 250,000. That's 1,650,000 hunters in three states. According to the all knowing Google there are currently 1,369,532 troops in the US army. That's right, taking into account the hunters in only three of the fifty states and leaving out the hobby shooters, gang bangers, and dedicated militia types leaves you with an armed body larger than the US Army. The number of functional firearms in the US is estimated to be close to the total population count. That means in theory the population of the US independent of it's government is capable of equipping an army of 300 million people. My point is only that you presume the armed populace to be smaller than it actually is.