Final answer:
The United States shifted from isolationism to international engagement largely due to its involvement in World War I, the interwar isolationist sentiment, the attack on Pearl Harbor, and the subsequent need for leadership in the post-World War II era. The rise of totalitarian regimes and global economic challenges further underscored the necessity for active U.S. involvement in international affairs to maintain stability and contain communism.
Step-by-step explanation:
The events that caused the United States to move from an isolationist nation to a more internationally engaged one primarily involved the world conflicts and the changing global power structures of the 20th century. The shift from isolationism became more pronounced after the United States entered World War I, a move that marked its first major departure from its historical reluctance to involve itself in European wars. However, during the interwar period, the U.S. returned to its isolationist leanings, largely fueled by the disillusionment with the outcomes of World War I and the economic focus of the Great Depression.
After World War II, with the old European powers weakened, there was a vacuum in international leadership that the United States stepped into, assuming the role of a superpower. The devastating attack on Pearl Harbor on December 7, 1941, decisively ended the United States' stance of non-interventionism and fully engaged it in the global conflict, eventually supporting the establishment of new international organizations and entering into alliances such as NATO to contain the spread of communism and maintain global stability.
Furthermore, economic and political crises abroad, and the rise of totalitarian regimes, underscored the interconnectedness of global affairs and the impossibility of the United States remaining unaffected by international events. These factors cumulatively influenced the U.S. foreign policy shift from a stance of isolation to one of active engagement, shaping the modern era of U.S. involvement in world affairs.
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