How did this happen?  America has changed. We did not see it coming.  And looking back, we don’t know how it happened.  Not so long ago, people spoke respectfully of the President, even if they had not voted for him. Not so long ago, attitudes toward guns, immigrants, abortion, Genesis did not divide us so deeply.  That world now seems lost, and we wonder what world is coming. I want to explore this polarization in this essay. Definitions I don’t use these terms in this essay, but they each are useful in naming some of the concepts in today’s polarization. American exceptionalism:  the notion that the U.S. is superior to other countries. Many who believe in exceptionalism also believe that the U.S. has a…