The QAnon movement is spreading around the world, turning an outlandish conspiracy theory revolving around President Trump into one of the nation’s most dangerous exports. Flags and banners brandishing one of the conspiracy’s mottos — “WWG1WGA,” an acronym for “where we go one, we go all” — dotted the crowd at a rally against lockdowns in Germany last month. And when Trump visited Japan in 2019, he was greeted by cardboard cutouts of the letter Q. These aren’t just isolated instances either. Researchers have found large QAnon communities in more than 70 countries. The original conspiracy theory was tightly focused...