The purpose of this article is to examine the formation of ASEAN+8 and its interaction with APEC from the perspectives of regionalisms. The United States began to restore its preponderance status in East Asia since President Obama declared himself the President of the Pacific Ocean. The most significant development in this regard includes the accession of the United States to East Asia Summit in 2011. Asia-Pacificism, led by the United States, will confront directly with East-Asianism in ASEAN. Due to the impacts of ASEAN+8, APEC would return its agenda setting back to economic concerns excluding security issues.