Except the vietnam war was lost, not due to the vietnamese outfighting the Military, but by hiding and taking potshots long enough that the resources used outweighed the benefit for continuing the conflict.

Compare that to a hypothetical tyrant US government, where the civilians would have to openly confront the government because hiding in a tree won't beat them on their own turf. The Vietnamese only won because of their terrain, their defensive fighting style, and public opinion of the war degrading. Any civil war against a tyrannical US Government would have none of those advantages and several disadvantages the Vietnamese didn't have.

Maybe actually learn something about warfare before making comparisons where there are none.