Which significant conflict did the United States participate in during the 1900s?

The significant conflict that the United States participated in during the 1900s is World War I. This global conflict lasted from 1914 to 1918 and involved many of the world's great powers at the time, divided into two main alliances: the Allied Powers and the Central Powers. The U.S. entered the war in 1917, after initially maintaining a stance of neutrality. America's involvement provided crucial support to the Allies in terms of both military resources and manpower, which ultimately contributed to the defeat of the Central Powers.

World War I is often seen as a transformative event in U.S. history, both politically and socially. The war influenced U.S. foreign policy and military strategy for decades to come, marking a significant shift towards a more active global role. This conflict also had significant domestic implications, leading to economic changes, shifts in social dynamics, and the eventual emergence of the U.S. as a world power.

In contrast, the other conflicts listed occurred in different contexts or time frames. The Spanish-American War, for example, was fought in 1898 and mainly revolved around issues of imperialism and the liberation of Cuba. The American Revolutionary War occurred much earlier, from 1775 to 1783, and established the