How many people might have been killed by nukes if the U.S. and our allies had not maintained our own stockpiles as a deterrent?
This is a really good point, and one that's often missed in the the debate over the so-called "insurrectionist" interpretation of the 2A.
During the Cold War, we had this idea called Mutually Assured Destruction. The Soviets wouldn't strike at us because it would spell the end of their nation, on a level worse than any concept of total war. On the other hand, we wouldn't strike them for the same reason.
(All of which led us into a couple of disastrous proxy wars, but that's another story)
The point is, we never sank to nuclear war. Deterrence
is the key word here.