The late conservative commentator Charles Krauthammer maintained of the U.S., “Decline is a choice.” This isn’t quite right with regard to Europe, whose great powers were kneecapped by the cataclysms of the early 20th century. France bore the brunt of World War I, suffering 1.4 million dead and 4.3 million wounded and a ruinous economic cost. As for Britain, stretched to the max, it got steadily eclipsed in power and influence by the United States as World War II progressed. The less said about Germany’s role in all this, of course, the better. And then the European colonial empires inevitably...