The question can be answered from three different historical perspectives: the orthodox, the revisionist, and the post-revisionist. The orthodox account blames the expansionary tendencies of the Soviet Union, well exemplified by the consolidation of Soviet-friendly regimes in Eastern Europe and the promotion of Communist ideology in Latin America, Africa and Asia. The US containment policy was a reaction to the Soviet aggression, warranting of the development of tight relations with Western Europe as well as intervening in the Third World to prevent Communist regime changes. Thus, it was primarily the ideological and political commitment to liberalism and democracy which informed US foreign policy. The revisionist accounts question the benign nature of the US by reinterpreting the historical trajectory of the Cold War confrontation. Given the post-war devastation in the USSR, it did not have the material base to launch a worldwide Communist expansion. Rather, the US is conceived as an expansionary state driven primarily by economic interests. The ‘open door’ policy among its allies was not an act of goodwill, but a means to open markets to US business. Further, the lack of ideological commitment to democracy was manifested in its subversion of democratic processes (e.g. Nicaragua, Guatemala) and its support for authoritarian leaders (e.g. Japan, South East Asia). Hence, US policies were rather shaped by economic and strategic interests. Finally, the post-revisionist accounts integrate the insights of the two accounts to offer a more balanced analysis.
What should be deemed more critical perhaps than weighing the evidence for one or another account is why these questions still get discussed and remain highly contentious? Beyond the ‘correctness’ of these accounts, the debate over US motivations is political (Orwell’s famous quote is pertinent here: Who controls the past controls the future; who controls the present controls the past). By contextualising these accounts (when, where, by whom) the political nature of historical narratives can be revealed. Further, these interpretations with their specific conceptualisation of US motivations shape the way we interpret US geopolitical activities in the contemporary era.