This dissertation examines how Latin American diplomacy helped shape U.S. officials’ response to revolutionary movements at the height of the Cold War. It explains the striking contrast between U.S. patronage of the Bolivian revolution and the profound antagonism with similar leftist nationalist movements in Cuba and Guatemala. Although U.S. policymakers worried that “Communists” were infiltrating the Bolivian Government, Bolivian diplomats convinced the Eisenhower administration to support their revolution. The dissertation demonstrates that even during the peak of McCarthyism, U.S. policymakers' vision extended far beyond Cold War dogmatism. This vision incorporated a subtle, if ultimately contradictory, appreciation of the power of nationalism, a wish to promote developmental liberalism, and a desire for hemispheric hegemony regardless of strategic and ideological competition with the Soviet Union. U.S. officials were eager to exploit the emerging force of third world nationalism and employ it to strengthen the “inter-American system.” The Bolivian revolutionaries presented their political project as copacetic to Washington’s wider regional goals, and thus managed to secure considerable freedom of movement to continue to pursue a radical revolutionary agenda and statist program of development, financed and enabled by hundreds of millions in U.S. aid dollars.