>A "Manhattan Project" would be building some shocking new technology that didn't previously exist.

I think that both Germany and USSR were not in the least shocked ... just the USA had the resources to finish it.

Well, USSR did finish, just 4 years later.

Maybe it was because we had all those immigrants working on it (e.g. Albert Einstein, Hans Bethe, and John von Neumann)!

There's a whole regiment of immigrants who worked on the Manhattan project, as we all know. We also know that the USSR obtained much of their knowledge on how to build the bomb through espionage.

Espionage? Gasp. The US would never do that to get ahead. I'm so suspicious of claims without external sources of provenance about American exceptionalism during the cold war that I take all if it with a large grain of salt. Back then, everything Russia said was propaganda, and everything the US said was truth from the mouth of god.