“I disagree. Culturally we used to have a great deal in common.”
Okay. Please explain 1776 when a large portion of the population wanted to remain with England and sided with our enemy (England) and again in 1861 when the northern states attacked the southern states both economically and physically. If those two examples are “a shared ethical outlook” then I’m totally confused.
Yes, we have had periods when all of the issues you explained were true, but if you study any history you will plainly see it does not last and there are periods when the opposite is true. We happen to be in one of those periods now!
That I don't disagree with. We are definitely in a period of great differences.