Why did the United States refuse to join the League of Nations?

The United States refused to join the League of Nations because, according to a group of U.S. Senators, the League infringed on the sovereignty of the United States. Some even argued that it might force the United States to send military forces overseas against its interests. Under the Constitution, all treaties must be ratified by the Senate, and the opponents of the League, who disagreed with it for the reasons mentioned above, also had a contentious relationship with President Woodrow Wilson, who had led negotiations that led to the League at the Paris Peace Conference of 1919. The opponents were led by Senator Henry Cabot Lodge, and their positions ranged from "irreconcilables" who dug in their heels for outright rejection to a more moderate faction that demanded changes in the language of the Treaty as a condition of ratification. Wilson refused to compromise with the moderates, and the Treaty with the League of Nations included was defeated in the Senate. So the opponents of the League placed American sovereignty over internationalism in the wake of World War I, and Wilson's intransigence in the face of their opposition doomed any notion of American participation in the League.