“The major threat of Europe at the moment is not Orban or Salvini, the major threat is that the E.U.’s institutional arrangement is unstable,” Mr. Ferguson said. Mr. Macron’s ambition has been to fix that; but there is no consensus backing him.

Whatever the future of Europe’s institutions, one big difference from 100 years ago is that the Continent is no longer at the heart geopolitics.

"A century ago, Europe was the center of the world — even if it was the dark tragic center of the world,” said Dominique Moïsi, a French author and thinker. “Today we might be back to tragedy but not to centrality.”

“History is moving elsewhere,” he said.

That, too, should be a motivation to shore up European integration, says the Reverend Musser in Alsace. One of his grandnieces is doing an internship in China, not Europe.

Bones, bombs and bullets remain in the soil of Alsace, a region switched back and forth between various incarnations of France and Germany five times between the Thirty Years’ War that ended in 1648 and the devastation of World War II.

Local residents joke that Alsatians still keep German street signs in their basements, just in case.

The Reverend Musser puts it this way: “Alsace is a reminder of how much has been won in Europe — and how much can be lost.”