So, right now, before any war that will be later labeled World War III for whatever reason, we have two WWIII's. You see, to some people, it's a war that hasn't happened yet, that will envelop the world the way the previous two (world) wars did. And that's where the description ends. On the other side, we've got people who say WWIII is the nuclear holocaust that is inevitable, or simply fictitious, that will end life on earth as we know it (I contend, in a tangent, that we don't even understand life on earth now).

That's how I view this thing called WWIII. Now then, in regards to nuclear war in general, and the fact that we had nuclear weapons during the Cold War and didn't use them: the entire point of nuclear war is that nuclear missiles, detonated anywhere in our atmosphere, will seriously impact life everywhere on earth. Who cares if the missile lands on American soil or not? What if it simply explodes in American air space? Or if it detonates in Europe somewhere and we only get the nuclear fallout in America? Or let's say we don't even get the fall out, but Europe's agriculture and way of life is now ... gone? The effects of nuclear war would be so wide spread as to make any missile defense shield totally pointless.