Which of the following events most clearly challenges the interpretation expressed in the excerpt?

The correct choice is the Washington Conference of 1921, as this event directly relates to U.S. foreign policy and its approach to international relations in the post-World War I era. The Washington Conference aimed to address naval disarmament and tensions in the Asia-Pacific region, reflecting a desire for peace and stability rather than aggression or isolationism. This emphasis on diplomacy and cooperation challenges interpretations that depict the United States as being solely focused on its own domestic issues or as adopting a policy of isolationism following the war.

The other options, while significant in their own contexts, do not challenge the interpretation in the same way. The stock market crash of 1929 underscores the economic vulnerabilities of the period, which could be seen as a pivot towards more inward, domestic concerns. The Prohibition era emphasizes social and cultural shifts rather than foreign policy stances. The New Deal represents a response to economic crises, also focusing on domestic policy adjustments rather than the international engagement highlighted by the Washington Conference. Each of these events is central to understanding U.S. history but does not challenge the same interpretation regarding foreign affairs and international diplomacy as prominently as the Washington Conference does.