Which country failed to join the newly created league of nations after the war ended? france united states italy great britain description?

The correct answer is the United States.

Even though the president of the United States, Woodrow Wilson, developed the idea of the League of Nations, the US did not officially join it. This is because Congress refused to pass the law that would make this joining possible. One of the biggest reasons why Congress did not want to join the League of Nations was because it would allowed the US to be dragged into foreign conflicts. After World War I, the US Congress thinks that developing a policy of isolationism will benefit the country.