Do not forget cherry picking in reverse. The more successful /well adjusted people stayed in Europe - it is the Podunk riff raff that had nothing to lose who decided to seek their fortunes in Amerika. They brought their Podunk/peasant expectations and traditions with them which became fossilized here for various reasons.
For me, meeting the Eastern European émigré communities in the US was like a journey back in time to the 19th century. Not everyone, of course, but quite a few. I hear the same about other immigrant communities (e.g. German aka Pennsylvania "Dutch" and Amish), Welsh (aka Appalachian hicks) etc. I also imagine the same can be said about Dutch in South Africa (aka Afrikaners).
Let's face it, for a long time the US was the human sewer of Europe - only with the rise of Nazism and cold war it became the destination of brain drain.
Wojtek