Earlier quoted context omitted.
Regarding just recent history, 2015-2021 is more divisive the 2000-2015, don't you think?
No - I think there's a class of people who weren't exposed to the divisions who're only now aware of it. In roughly chronological order: Anti-"war on terror" demonstrations, The Dixie Chicks being canceled, freedom fries, the handling of Katrina, the divisive 2008 presidential campaign season, the backlash to Obama's presidency, the rise of the Tea Party, the Benghazi investigation, Sandy Hook, birtherism. I probably…
Of course, to mention specifics would be partisan, and partisanship is culture war, and culture war is killing us so who can even say what? We'll just say that somewhere around the end of Obama's term it seems like maybe something happened.