Are you blind? Don't you think part of the reason why we haven't been attacked in such a long time has to do with the fact that everyone knows this country is armed?
Absolutely not. The list of countries that don't have an armed citizenry that also haven't been invaded is much longer. The main reason why the US has not been invaded is its strong military. Any invading force that can get by the US military is not going to be worried by its armed citizenry, not matter how many times you watch Red Dawn