You can always tell what, or more specifically who, America feared most based on movie villains. For a long stretch, Germans and Russians were the go-to villains. Asians, scary looking black men and in the last decade, Eastern Europeans have played many a bad guy (and in Die Hard 3, girl).
I was just watching Back to the Future (ok, I still am) and Doc shrieks in horror, "They found me!"
"Who?" asks Marty.