Highlight: Sorry, no, that's complete nonsense. Which moderate socialist regimes were emigrants to the USA fleeing? There really weren't any until well after WW2, by which time relatively few Europeans (except from the most war-ravaged or poorest countries) were especially interested in emigrating to the USA -- assuming, of course, that they'd have been let in.
Most emigrants from Europe were fleeing poverty under traditional regimes, where the rich did their best to make sure that the poor stayed poor; or religious persecution (some of them, of course, merely wanted to be the ones doing the persecuting); or simple failure in their own lives.
Also, consider the phrase "Some of us don't want your moderate socialism." Very true. But others do; and many more would want it if they could see the way that most Europeans (not just the rich) live. For just one example, it's quite nice not to live in permanent fear of bankruptcy from medical bills and to know that infant mortality rates where you live are 30-70% better than in the United States (5.9 in USA, 4.43 in the EU as a whole, 3.34 in France where I live). Those figures, incidentally, come from that well-known left-wing organization, the CIA:
https://www.cia.gov/library/publications/the-world-factbook/rankorder/2091rank.html
Thanks for reminding me of what the abbreviation OWS stood for, incidentally.
Cheers,
R.