NEW YORK - We are in a protracted period of international transition, one that began more than two decades ago with the Cold War's end. That era of strategic rivalry between the United States and the Soviet Union gave way to one in which the US possessed far greater power than any other country and enjoyed an unprecedented degree of influence. That American unipolar moment has given way to a world better described as non-polar, in which power is widely distributed among nearly 200 states and tens of thousands of non-state actors ranging from Al Qaeda to Al Jazeera and from Goldman Sachs to the United Nations.