No level of armament garuntees success in a war. Any level improves your chances of winning.
So the amendment improves the chances of the people winning compared to being disarmed should they ever have to fight their own government. That alone is sufficient.
I would argue that being armed, even against superior firepower would **significantly** improve the peoples chance of success. Consider that it is very possible in such a scenario that the military would have **much** smaller numbers overall than the whole of the US population. Assuming none of the military would flee should the govt become tyrannical you are talking about 600x more armed civilians than military. I'd say being less armed but having a 600:1 advantage in people would ultimately put the american people at the advantage.