The United States is a sports-loving nation, but there's a blind spot in its devotion. Although millions of Americans play soccer, they show little sustained interest in watching it in person or on television. That may change after the 52-game World Cup soccer finals are staged in the U.S. for the first time, starting in mid-June. An estimated 2 billion TV viewers worldwide will watch the July 17 championship game at the Rose Bowl, reaffirming its status as the world's premier sporting event. Meanwhile, organizers of a new professional U.S. soccer league are counting on World Cup enthusiasm to boost the venture's launch next spring. But the troubled history of pro soccer in the United States offers scant hope for instant success.