I agree with the generational approach. People who remember ravaging anti-semitism, whether in Russia, Germany, or USA, behave accordingly. Also, the “melting pot” pre-60s view made it very difficult not to look like others, and corresponding reaction from others. Even in our time, Jews in Paris, I think are more careful walking around identifying openly as Jews.
Years ago, someone finishing medical school, sporting a kippah, of course, had an interview with a doctor in NYC. The doctor did not have a kippah, but at some point walkling around hospital, he oured himself a cup of water, went with this guy into an empty office, closed the door, and took a kippah from his pocket to say a brocha.