On Sunday afternoon, at a sold-out stadium in Frankfurt, the U.S. soccer team will attempt to defeat Japan for the Women’s World Cup championship. On Monday, and in the days, weeks and months to follow, the American bunch will confront a more imposing endeavor: convincing the public that women’s soccer has more to offer than international thrills. With dramatic victories against Brazil and France in the past two matches, the players reintroduced the sport to casual sports fans, won the hearts of millions of Americans and likely will inspire a new generation of young players.