And even if these autocracies would be stupid enough to use nuclear weapons then we’ve still got systems for intercepting ballistic missiles in-flight in the upper atmosphere.

Hol’ up. We’ve got systems. None that actually work. Hitting an ICBM is like hitting a needle in a haystack with a needle in a haystack. I’m sure we’ve made progress since the 80s Star Wars programs. But even if a fraction of the nukes detonate where they are supposed to, that’s the end of civilization.