As factories closed or were automated, the social structure of working-class towns and neighborhoods was undercut. Men who used to be role models found themselves out of work. Many took low-wage service sector jobs they perceived as demeaning. Drug and alcohol use rose. There was talk about how things had changed for the worse. This was the realization that a social world was gone.

Last month’s presidential election has collective trauma written all over it. For working-class white people whose communities had been hollowed out by the decline of manufacturing, the rhetoric and promises of Donald J. Trump’s campaign offered a salve. He vowed to restore the world they had lost.

But those who voted for Hillary Clinton may now be experiencing collective trauma of their own. In the aftermath of the election, they have been walking around in a daze. Some of this is because forecasts based on problematic polling strongly predicted a Democratic win. Some is fear or uncertainty about the future. But there’s more to it than that: For progressives, moderates and “Never Trump” Republicans, the political order they long took for granted — defined by polarization, yes, but also by a commitment to basic principles of democracy and decency — is suddenly gone.

In recent decades, Democrats and Republicans rarely agreed on substance, but all candidates for major office were expected to adhere to fundamental ethical norms, like “don’t threaten to jail your opponent” and “don’t celebrate sexual assault.” Mr. Trump’s victory signals that that world, with the assurances it offered that there were some lines those seeking power wouldn’t cross (or that the American electorate wouldn’t let them cross), is no longer. Rightly or wrongly, memories have been activated of historical traumas linked with anti-democratic politics, such as the emergence of fascism in interwar Europe and the rise of Senator Joseph McCarthy in the 1950s.

The title of Mr. Eyerman’s book about Katrina — “Is This America?” — is a question many have been asking lately. It’s a telltale sign of collective trauma, a grasping for identity when the usual bases for community aren’t there anymore. If research on other collective traumas is any indication, it may take years, and a great deal of political imagination, for us to figure out where to go from here.