U.S. Shift to Imperialism in the Late 19th Century

During the late 19th and early 20th centuries, U.S. imperialism manifested in various forms, often justified by a combination of economic interests, national security concerns, and ideological beliefs. A key moment in this era was the acquisition of overseas territories, such as during the Spanish-American War in 1898. American expansion into territories like Puerto Rico, Guam, and the Philippines raised critical questions about the nation's role on the global stage.

In this context, which of the following events most directly demonstrated a shift in U.S. foreign policy towards an active imperialist agenda during the late 19th century?