What Unifies Americans, and What Doesn’t

There are several good answers to this excellent question.

The first and obvious is that an attack by an exterior group to one’s own naturally pulls the assaulted group together, despite any internal differences that may exist.

A more nuanced, though also important answer is that this is not the same country it was 20 years ago.  We didn’t have a contingent of tens of millions of ignorant people who, by virtue of what they can find on the Internet over a period of a few hours, believe they are overnight experts in a certain subject matter.  These are disciplines in which the true scholars have spent their entire adult lives studying, posing hypotheses, conducting rigorous experiments, drawing conclusions, writing comprehensive papers, getting them peer-reviewed, and publishing their ultimate findings.

We live among countless fools, where that was not the case in 2001.