Well, K-Mac, our behavior such as you describe started in 1776. If you didn't like the way the revolution was headed, you were in for a tough time. Lots of folks left. Same way at the time of the Civil War. When has it been different?
There have also been plenty of times when people did not necessarily feel the way they were supposed to be feeling, like during wartime. There was no general animosity against the Germans before WWII, as best as I can tell. Of course, Americans really aren't that great at hating other people. That is, people in other countries. We save our fear and hatred for our fellow citizens. We aren't pure enough in any sense of the word, nor are we exceptional. That's not to say we aren't different.
There is both a lot of group-think and wildly independent thinking here (including on this forum), although independent thinking carries considerable risk (including on this forum). It is a rich mixture. But one way to get a good crop is to use lots of manure.
Shoot low, sheriff. They're riding Shetlands!
Underneath the starry flag, civilize 'em with a Krag,
and return us to our own beloved homes!
Buy War Bonds.