This essay examines the role that nuclear weapons have played in Northeast Asia in creating a system of inter-state relations based in part on nuclear threat and the impact of North Korea on that system. The US-led alliances that rest on extended nuclear deterrence have been characterized as hegemonic in the forty years of Cold War in the Gramscian sense of hegemonic, that is, allied elites accepted US leadership based on its legitimating ideology of extended nuclear deterrence, institutional integration, and unique American nuclear forces that underpinned the alliances. A crucial aspect of American nuclear hegemony in Asia was the guarantee that the hegemon would ensure that no adversary could break out of the system after China's 1964 successful nuclear test, as expressed by the Non Proliferation Treaty and IAEA safeguard system. The failure of the United States to stop and now reverse the DPRK nuclear over the previous two decades threatens its hegemonic leadership in Northeast Asia, and is linked to the decreasing ability of American power to shape events in other proliferation-prone regions such as South and West Asia.