You honestly believe that if the government turned as tyrannical as you fear, that an armed populace would be able to stop them?  If you use the example of either Viet Nam or Afghanistan both of those populaces had outside support that supplied both heavy weapons and training, and by heavy weapons, I mean artillery and/or MANPADs among other things.

The idea of an armed militia being able to stop the government ended decades ago.  With the advent of aircraft and tanks, we are no longer in a place where we can expect to be able to fight back and actually win, no matter what fantasy world you may be living in.