I do think that the U.S. has a serious malady, but a big part of this is deciding that facts don't matter. Just opinions.

And you've caught the disease as bad as anyone. C'mon. Don't fall for that! Check your stuff.

Only 55% of white voters voted for Trump in 2020, not 79%: https://www.pewresearch.org/politics/2021/06/30/behind-bidens-2020-victory/

Even white men in 2016--the most strongly pro-Trump group identified--only gave 62% of their votes to Trump.

The rest of your points--well, they may have some merit. But if you are reasoning to those points from facts then it's very important to get the facts right. (If you're doing the other thing, where you get the opinion first and then fill in facts that seem to fit, it won't much matter if the facts are wrong...but then they're not very useful for convincing anyone of anything because the conclusion doesn't actually depend on them!)

And I still don't see how this fully explains how wildly popular improvements didn't get enacted before attention fizzled away.