United States (U.S.) policy towards Southeast Asia has undergone dramatic shifts in the post-war era. During the Cold War, U.S. policy towards the region was framed in terms of its doctrine of containment. Fear of Southeast Asian dominoes falling to communism led the U.S. to intervene extensively in the region, most notably by fighting the Vietnam War. After the end of the Cold War, the U.S. adopted an overarching policy of liberalism towards Southeast Asia, leading it to promote political democracy and economic openness in the belief that security would be assured because democracies do not fight one another. Since the events of 11 September 2001, Southeast Asia has been designated the second front in the global war on terror (GWOT). Currently, some Bush administration officials appear to be moving towards a policy of treating China as a strategic competitor, rather than a strategic partner. If this were to occur, Southeast Asia might once again become an arena of great power competition, giving the U.S. a new rationale for engagement in the region.

These dramatic swings in U.S. policy towards Southeast Asia are in large part a function of the nature of U.S. interests in the region. Located halfway around the world from the American mainland, the U.S. has few historical links to the region outside of its colonial relationship with the Philippines. Distance and the lack of traditional ties mean that U.S. interests in the region are strategic, not direct. The U.S. has an interest in keeping open the vital sea lanes of communication that transit through Southeast Asia. It has an interest in ensuring that the region does not fall under the hegemony of another external power. It has an interest in preventing the spread of transnational threats including terrorism, drug trafficking, and diseases such as AIDS, Severe Acute Respiratory Syndrome (SARS) and avian flu from Southeast Asia to the U.S.

Precisely because its regional interests are indirect, U.S. policy towards Southeast Asia is driven largely by its overarching grand strategy, rather than by a concern with the well-being of local states. The dynamics of U.S.- Southeast Asian relations, therefore, are a function of the ways in which Southeast Asia fits into the broad U.S. strategic doctrine, the types of policies the U.S. adopts towards the region, and how local states respond to them.