Name one war fought by the U.S. during the 1900s.

World War II is a significant conflict that took place during the 1900s, specifically from 1939 to 1945. It involved many countries around the world, including the United States, which entered the war after the attack on Pearl Harbor in December 1941. This war led to major global political changes, the establishment of the United Nations, and significant advancements in military technology. The U.S. played a critical role in both the European and Pacific theaters, and the outcome of the war had lasting impacts on international relations and the status of the United States as a global superpower.

The Civil War, while an important part of American history, occurred from 1861 to 1865, making it outside the specified timeframe of the 1900s. The Mexican-American War, which took place from 1846 to 1848, also predates the 20th century. Similarly, the War of 1812 occurred from 1812 to 1815. Therefore, among the choices, World War II is the only one that aligns with the 20th century, demonstrating a major military engagement that involved the U.S.