"The Empire Strikes Back" or the shift and from "The Net interprets censorship as damage and routes around it" to "de-platforming works"; its not over its just getting started.

The breakdown of the ability of either side to actually listen, either to the other side or to the population as a whole.

Second, but probably related: The increased dysfunctionality of Congress.

The identity politics of both sides. We are all human and want the best for the world, yet people imply otherwise based on race, sex, and sexuality, not to mention political leaning. It is bigotry plain and simple.