In a sense, the Project wasn’t really American.
Nonsense. It was DISTINCTLY American. Thoae scientist were wilfully and happily here instead of their countries of origin exactly like everyone else who came here here since time immemorial. They were here because America is America.
Actually, quite a few were here because the Germans took over or were about to take over their former countries and came to the Allies because they had no other choice than enslavement or death - go look at Bohr’s bio, for example. Or Enrico Fermi - he used the Stockholm trip to accept the Nobel Prize as a way to get out of an Italy that was likely to shoot him due to new laws. He hopped the first flight out and ended up in New York.