Despite the high dependency on nuclear energy for electricity and a vast number of nuclear weapons in East Asia, a lack of regional atomic energy organizations dealing with nuclear safety and security brings about instability and constant tensions in the region. One may question: why is there no EURATOM-type regional nuclear institution in Asia?This article argues that collective identity plays an important role in regional groupings, especially on the issue of nuclear power. Thus, it focuses on eclectic stance that grants constitutive processes causal relevance, so called ;;collective identity.” Racial, historical, political, and cultural factors all together significantly affect the foreign policies of the United States toward Europe and Asia respectively. Also, this article analyzes the differences in mutual identification of the U.S. vis-à-vis Europe and Asia in terms of regionalism and the interests of U.S. decision makers.From American perspectives, the logic in choosing multilateralism over bilateralism in Europe was a matter of course based on their perceptions and collective identity that they have been built over hundred years one another. On the other hand, Asia has been still foreign to the US with dynamic political structure and different threats. As a result, proposals for an East Asian version of EURATOM ended in failure and quickly took the shape of bilateral military agreements with the hub-and-spoke security order. Especially, when the proposals for regional collective actions contained the delicate issues such as reprocessing and a possibility of creating nuclear weapons, each party should entirely trust each other and share the certain level of collective identity with shared interests. The case of renegotiating the U.S.-EURATOM agreement and the attempt of a EURATOM-type Asian nuclear collective initiative, so-called ASIATOM in 1990s clearly show the different approaches of the US based in terms of multilateralism in Europe and Asia respectively.