I’m not worried about a civil war. And as far as the rest of the world picking at us... we always have the option of MAD: nuke Russia, China, etc.
Do a Samson option and pull the pillars down. If America doesn’t survive, we could guarantee the rest of the human race is reduced to a pile of radioactive ash.
I don’t believe MAD could work with man at the helm. Not without a safeguard ensuring that if X (Where X is a nation with nuclear weapons) were about to be obliterated , the missiles would be fired in return.
Put yourself in that position. I don’t care who you are. You’re about to turn the key, you have authorization from the President and he has given you your launch codes. Could any man do it? You can say you would all you want. But you know what happens. That’s it. You are tasked with ending the human race. If you push that button. It’s over. No one can be saddled with that responsibility. It has to be initiated by a dead-switch. Or there is no such thing as MAD.
There have been a few documented instances where those on watch were presented with situations where they thought the nukes were flying. About to fire back, but suddenly stopped. During the cold war it happened at least once that the public knows of.