Britain's departure meant the end of an era. France's departure would mean the end of the EU. After Grexit and Brexit, the next crisis to confront the European Union will be Frexit. It will prove to be the worst of all. While dramatic, the Greek tragedy had a limited run. While seismic, the British divorce will not necessarily upend Brussels. But for historical and institutional reasons, a French crisis would be cataclysmic. The midwife for the EU’s birth, France now risks becoming its gravedigger. The ruin and rubble of World War II had not been entirely cleared when France laid...