March 19 (UPI) — As millions of Americans fill out brackets for March Madness, the annual NCAA basketball tournament offers more than collegiate drama — it highlights the quiet power of sport to build bridges across cultures and borders. From the Cold War's ping-pong exchanges that helped thaw relations between the United States and China to the rare sight of athletes marching under a unified Korean flag at the Olympics, sports has repeatedly opened diplomatic channels when politics stalled. As geopolitical fragmentation deepens and Washington launches its U.S. Decade of Sports, policymakers may find that sports diplomacy offers an overlooked…