It’s been 10 years since Angela Merkel, as German chancellor, memorably declared “Wir schaffen das” — “We can do this” — in the face of the mass migration crisis sweeping Europe. Last week The Wall Street Journal reported, “For the first time, populist or far-right parties are leading the polls in the U.K., France and Germany.” Similar parties are already in power or in government in Hungary, Italy, the Netherlands and Sweden, to say nothing of the United States. To say the West’s turn...