A significant portion of the WW2 scientists were refugees from _before_ the US joined the war but after persecution had started. https://ahf.nuclearmuseum.org/scientist-refugees-and-manhatt...

(later notable entry: Andy Grove, Intel CEO, was born Andreas Grov:

"By the time I was twenty, I had lived through a Hungarian Fascist dictatorship, German military occupation, the Nazis' "Final Solution," the siege of Budapest by the Soviet Red Army, a period of chaotic democracy in the years immediately after the war, a variety of repressive Communist regimes, and a popular uprising that was put down at gunpoint... [where] many young people were killed; countless others were interned. Some two hundred thousand Hungarians escaped to the West. I was one of them")

I think there is a difference between bringing in key proven talent at the apex that’s already proven itself and talent that needs to be developed. Both the US and USSR picked up proven talent from the Nazis, they weren’t siphoning up green talent on the hopes they’d develop into good scientists. We have our own population we often overlook and misdirect into Hollywood entertainment rather than achievement.