The surge of regionalism in recent years would seem almost by definition a development outside the sway of the United States, the global hegemon. Regionalism prioritizes the local; a hegemon exemplifies the global. Yet, at least since the end of the Second World War, the United States has been the most important actor in the global evolution of regional order1 and governance.2 Indeed, it is difficult to discuss almost any regional order without reference to the role of the United States. America is the world’s ‘omnipower’ in its involvement in almost all efforts at regionalism. The rise of new regional powers and the emergence of regional governance are also the product of many factors that have nothing to do with the United States. Yet, any effort to map and understand the trajectory of regional orders requires an understanding of the role of the United States therein.