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

The choice of World War II as one of the wars fought by the United States in the 1900s is accurate due to its significant impact and involvement. The U.S. entered World War II after the attack on Pearl Harbor in 1941, participating alongside Allies against the Axis powers until the war concluded in 1945. This conflict played a crucial role in shaping global politics, economies, and military strategies throughout the latter half of the 20th century.

While the other conflicts mentioned are also significant, they do not fit the criteria of only one war fought in the specified timeframe. The Civil War took place earlier, from 1861 to 1865. The choice indicating both World Wars implies the inclusion of World War I as well, which could complicate the answer since it requests recognition of just one specific war.