I would suggest that this is because the majority of top scientists working on the bomb were Jewish. The United States received a massive windfall of top talent from European Jews fleeing the anti-semitism of Nazi Germany.
There is an excellent book on the topic called "The Making of the Atomic Bomb" by Richard Rhodes. I urge anyone who hasn't read it to get a copy and read it.
Rhodes’ two books and all the info on the spies was where I got most of my info from, he spent a LOT of time in “Dark Sun” on it, almost too much.