Final answer:
The Allied victory in World War II marked the pivotal event that established the United States as a world superpower, leading to its influential role in international affairs and the onset of the Cold War.
Step-by-step explanation:
The historical event that led to the United States becoming a world superpower was the Allied victory in World War II. This monumental event saw the U.S. emerge as an economic superpower as its cities and industries were largely unscathed by the conflict. Following the war, the United States was pivotal in rebuilding war-torn Europe and Japan, and it began constructing international alliances to promote global peace, effectively shaping the new world order. This era also marked the start of the Cold War as the U.S. and the Soviet Union emerged as the two dominant world powers, competing for influence across the globe.