"What would have happened if the US had stayed out of WWII?"
Neither of us know the answer to that.
And you 'assuming' I have no sense of geopolitics means nothing.
Do you realy believe that the Monroe Doctrine could work today (or in the 20th century)? What would have happened if the US had stayed out of WWII? The Nazis and the Bolsheviks would have divided the Old World between themselves or the Nazis would have defeated the Bolsheviks. Would that have been beneficial to the US? Wouldn’t the Nazis have become a mortal threat to the US? The similar situation could have happened if NATO hadn’t been established to counter the Soviet threat after WWII and the Soviets had seized all Europe.
The Monroe Doctrine could work in the 19th century because Great Britain protected the seas. It can’t work these days.
You have no sense of geopolitics.
"What would have happened if the US had stayed out of WWII?"
Would you be willing to send your own countrymen to the U.S. to protect our borders and take care of our problems, while your country has issues that are more important to your country than getting involved in other country’s problems?