During the past decade, as internal struggles have preoccupied the U.S., the rest of the world hasn’t been standing still. China has risen, as has populist nationalism—and so too, it turns out, has anti-Semitism.

The latest global survey conducted by the Anti-Defamation League finds that anti-Semitic attitudes have increased significantly since 2015 in Central and Eastern Europe, which before the Holocaust was home to most of European Jewry. According to the ADL’s 11-question index, in use for more than 50 years, the share...