The USA didn't join the League
Wilson was very ill by this time, and Congress rejected the League.
The USA never became a member. These are the reasons why:
1. The people of America hadn't liked the Versailles treaty, and refused to accept it. They thought the League of Nations was connected to it.
2. They believed it would be too expensive- many people wanted to stay out of Europe, and wanted only to worry about USA affairs. This attitude was called isolationism.
3. Many thought that all people should be free under democracy, and weren't willing to be dragged into wars to help countries like Britain and France keep undemocratic colonies.
4. Wilson's political enemies wanted to make him unpopular, and get rid of him.
The League Wasn't Powerful Enough
1. Britain and France were in charge, but neither country was strong enough after the War to do the job properly.
2. Economic and military sanctions could only work if a powerful nation like the USA was applying them, but most countries were busy rebuilding.
3. Germany and Russia were not allowed to be members when the League was first formed.
4. The League had no army of its own, and most members didn't want to commit troops to war. Some countries like Italy were quite prepared to ignore the League if they wanted to.
5. The organisation was a disaster- in the Assembly and the Council everyone had to agree before anything could happen. The Court of Justice had no powers to make a country act.
The League Failed to Sort Out the Corfu Incident 1
The Italian leader Mussolini occupied the Greek island of Corfu in 1923 after the murder of an Italian diplomat. He demanded financial compensation and an apology from Greece. The League demanded that the money should be paid to them- but Mussolini got the decision overturned and received both the money and the apology he wanted. The League was seen to be weak