As the world's institutions and analysts have spent two decades proclaiming the arrival of multipolarity, the actual distribution of comprehensive power has quietly moved in the opposite direction. The United States and China have not merely remained dominant — they have together widened the distance between themselves and every other state, concentrating economic output, manufacturing, and research capacity at a pace that outstrips the rise of any third contender. What the end of American unipolarity produced was not a diffusion of power among many, but the emergence of a second superpower —