The Sunday before last, Paul Van Haver, the Belgian dance-music star who, as Stromae, plays to multitudes in Europe but is largely unknown here, was in a taxi, passing through Times Square on his way to watch a World Cup soccer match between Belgium and Russia. At a red light, one of Van Haver’s countrymen, whose fright wig was dyed black, yellow, and red, the colors of the Belgian flag, crossed in front of the cab, and Van Haver—a tall, slender, unassuming twenty-nine-year-old, of half-Rwandan descent, dressed in a pastel-blue cardigan and what he called “grandfather moccasins”— recalled that, two days earlier, midway through his first New York concert, he had jokingly described Belgium as “a really small country just next to France—like, a ridiculous country.” From the stage, he…