Why US did not join League of Nations?
Similarly one may ask, why the United States did not join the League of Nations?
The League of Nations was established at the end of World War I as an international peacekeeping organization. Although US President Woodrow Wilson was an enthusiastic proponent of the League, the United States did not officially join the League of Nations due to opposition from isolationists in Congress.
Then, why the US should have joined the League of Nations?
The United States should absolutely join sign the Treaty of Versailles and join the League of Nations. The United States fought in World War 1 and many Americans lost their lives defeating the Germans and their allies. The League of Nations and the Treaty of Versailles will put an end to this ugly and terrible war.
The League of Nations aimed to stop wars, improve people's lives and jobs, encourage disarmament and enforce the Treaty of Versailles. Judged against these aims, the League was quite successful in the 1920s. It stopped border disputes turning into wars.