Answer: There were many different reasons why the average americans would be against the League of Nations. The major reason is the strong culture of isolationism inside the U.S. Many average Americans only supported U.S. intervention during World War 1 because of the sinking of the Lucitania. After World War 1 ended many Americans desired to go back to isolationism and did not want to be involved in European issues anymore. There were obviously other reasons, however, the culture of isolationism was the strongest.