original_query: What was the significance of the U.S. becoming a member of the Southeast Asia Treaty Organization (SEATO) alliance in 1954?
query: What was the significance of the U.S. becoming a member of the Southeast Asia Treaty Organization (SEATO) alliance in 1954?
answer: The U.S. joined SEATO in 1954 as part of its efforts to contain the spread of communism in Southeast Asia, following the end of the First Indochina War and the French defeat at Dien Bien Phu.  This membership reflected the Domino Theory, which posited that the fall of one Southeast Asian nation to communism would lead to the fall of others.