In the 1950s the US had lots of foreign scientists.
In fact if the US hadn't had its huge influx of foreign scientists fleeing the Nazis, who knows where we'd even be today.
You're not wrong, but let's not forget that some large number of scientists (cough Werner von Braun cough) were fleeing prosecution as Nazis.
Then there would be someone else who'd come. Considering they came to US and not to other places out of Europe. It would mean conditions were favorable in US.