The United States failed to contain communism to Vietnam as the Communist Party took power not only in South Vietnam but throughout Southeast Asia. Ironically, however, this development proved wrong one of the tenets of the American containment philosophy: that communism represented a monolithic threat to American global interests.

After a decades-long stalemate in Vietnam, the United States withdrew from the region in 1973 having saved face with as ostensible peace agreement (which both sides knew would not stand). North Vietnam invaded South Vietnam in 1975 and reunified the region under Communist rule. In short order, the Communist Parties of Laos and Cambodia, themselves involved in a long struggle with the government, both took power in 1975. In a sense, then, the "domino theory" of Eisenhower's administration proved true. By withdrawing support for South Vietnam, the United States witnessed one nation after another falling to the Communist Party in the region.

Once in power, however, the various Communist Parties proved to be more nationalistic than monolithic. Americans had feared that one unified Communist Party would control Eastern Europe, Korea, Southeast Asia, China, all ruled by Moscow, and that Communism would continue to spread to places like Thailand and so on. In reality, the Khmer Rouge regime of Cambodia feared that the Vietnamese would try to build a single, Southeast Asian Communist confederation ruled by Hanoi, leading to border skirmishes and eventually a full blown Vietnamese invasion of Cambodia in 1978, just a few years after communist took hold in Southeast Asia. After Vietnam installed a puppet government, the divisions within the communist movement became even clearer, as China protested and even launched an abortive invasion of Vietnam. Communism did not spread into Thailand, as American policymakers had feared.