What happens: whatever the people, who are now in control of
'whatever superpowers the US left behind', decide.
Look, I know its hard for you to not feel right without insulting anyone, but I've actually read a metric fuck-ton of history, know a few words in a few languages, and am generally not an ignorant 'incorrect-oid'. There is no truly correct/incorrect point of view, when it comes to killing humans. Fact: we don't need to do it. We do it because we want to.
Here's a thought experiment for you, American. What would happen if, instead of putting your citizens in debt to the tune of $TRILLIONS of dollars, every year, while funding active warfare on multiple fronts around the globe, for the last 80 years, the good ol' folks of the USA had instead built massive super-weaponry that delivered schools, water-filtration, and medical facilities, with awesome overwhelming power, to the people who needed it.
Instead of, you know, dropping one bomb every twenty minutes for the last .. umm, lets just say, at least .. decade?
Hmm?
You think its so easy? Lets see that B1 bomber re-purposed to drop the write kind of supplies that makes war unnecessary, not "invetible", as your formidable culture seems to want the rest of us to think it is ..