The world could have had real peace, if, after WWII, the US had been liberal with nukes for nations that stepped out of line. We could have announced that any country that tested a nuclear device would have been nuked by the US. That means Russia, or China. Heck, it should have meant the UK too. Only one country in the world should have nukes and the primary responsibility of that country should have been to make sure that no one else ever got nukes.
Secondarily, we could have nuked a country that invaded across an international border (Saddam in Kuwait). No boots on the ground. Not for the US. Never. But we could have nuked the people who needed nuking.
The continental US would have been untouchable. Our defense budget could have been very small. And the world could have had peace.
Given the state of the art in those days (40s-50s) ... had anyone followed your plan the world would be awash in highly radioactive fallout, with the few surviving enclaves of humans struggling to find something to eat beneath vast dark clouds and subfreezing temperatures as the hundred year nuclear winter slowly encroached.
When you declare war, your intention is to defeat an enemy state -- even to the point of obliterating it.
The U.S. has no intention of ever "defeating an enemy state" these days. Now, we are a global empire whose primary purpose is to occupy these countries -- which means obliterating them defeats the whole purpose of going to war against them in the first place.
But they didn't, so we're in the current mess.
Our leaders are, and have always been, shortsighted and we suffer the consequences.