Name one war fought by the United States in the 1900s.

World War I is considered a significant war fought by the United States in the 1900s. The U.S. entered the conflict in 1917 and played a crucial role in the Allied victory over the Central Powers. This war marked a pivotal point in U.S. history, as it was one of the first times the country engaged in a large-scale conflict overseas, which ultimately influenced its role in global affairs in the subsequent decades.

The other wars mentioned occurred either before the 1900s or were not primarily associated with that century. The Civil War took place from 1861 to 1865, the War of 1812 was fought from 1812 to 1815, and the Spanish-American War occurred in 1898. These conflicts, while significant, are not representative of wars fought during the 20th century, which clearly includes World War I.