One way to think about all these moves is that they were attempts to give Europe many of the attributes of a single nation without formal political union — at least not yet. The more or less explicit hope of many in the European elite was that technical and economic integration would gradually foster psychological unification, and eventually pave the way for a United States of Europe.

And for a long time the project worked very well, as Europe grew steadily more prosperous, peaceful, and free. But how would the process deal with setbacks? After all, the European project was creating ever-growing interdependence without creating either the institutions or, despite elite hopes, the sense of political legitimacy that would be needed to manage that interdependence if things went wrong.

Which brings me to the disasters.

At first sight, the financial crisis, the refugee crisis, and the terrorist attacks might not seem to have anything in common. But in each case Europe’s ability to protect itself turns out to have been undermined by its imperfect union.

On the financial crisis: There’s widespread consensus among economists (though not, alas, among politicians) that Europe’s woes were mainly caused by mood swings among private investors, who recklessly poured money into southern Europe after the creation of the euro, then abruptly reversed course a decade later. Yet something similar happened in America, too, where money first poured into mortgage lending in the “sand states” — Florida, Arizona, Nevada, California — then took flight. In the U.S., however, the pain of that reversal was limited by federal institutions, ranging from Social Security to deposit insurance. In Europe, unfortunately, the cost of bank bailouts and much more fell on national governments, so that private-sector overreach soon spilled over into fiscal crisis.