I find the parent poster's wholesale purchase of American exceptionalism... optimistic, to be kind. But I also think you're over optimistic thinking it is a forgone conclusion that any military, regardless of any bill of rights, would be able to easily crush a popular revolt. That depends upon a lot of factors.
Of course, and the counterpoint is that there have been revolts that toppled governments. The issue is that pro-gun people take it as a given that the US army, a body of people with both vastly more training and more firepower than the population, will have trouble with it.
