There are many factors that led to World War 1, but American isolationism was not one of them. The war was primarily caused by a combination of factors, including the rise of nationalism, militarism, and imperialism in Europe, as well as the complex system of alliances between European countries.
American isolationism did, however, play a role in the United States' decision to enter the war. By 1917, the war had become increasingly costly and destructive, and the United States was concerned about the potential impact of a German victory on its own interests. In addition, the sinking of the Lusitania and other German attacks on American ships and citizens helped to turn public opinion in the United States against Germany and in favor of entering the war.