The United States has ridden -- and tamed -- the wild global tiger since the end of World War II. The frantic ride has been dangerous, to us, but a boon to humanity. At the same time, America's leadership role has been misrepresented and misunderstood abroad and at home, including by some of our country's own leaders. Accordingly, our current president, Barack Obama, has decided to climb down from the tiger, with the certain consequence that it will run wild again. The crowning achievement of postwar American policy was the defeat of Soviet communism. After the fall of the Berlin...