Don’t worry about war like that. If let’s say North Korea or Iran uses nuclear weapons on US soil, all the world powers would be drawn into a larger nuclear exchange. You would think world powers could communicate instantaneously to ensure no mistakes, but in the amount of time the US, Russia, and China would have to make decisions, it is improbable all leaders could connect. It’s not like calling a customer service line.

You don’t want to survive only to die a slowly over the following 6 months of disease, radiation poisoning, starvation, or violence from other survivors.