The U.S. involvement in World War I was significant as it marked America’s emergence as a global power. Entering the war in 1917, the U.S. provided fresh troops and substantial resources, helping to tip the balance in favor of the Allies. The American Expeditionary Forces played an essential role in key battles such as the Meuse-Argonne Offensive. Additionally, U.S. involvement facilitated the establishment of the League of Nations, although the U.S. later chose not to join. The war shaped America's foreign policy, leading to a period of isolationism, and laid the groundwork for the nation’s involvement in future global conflicts.