In 1919, when the US, France, and Britain hammered out the Treaty of Paris that supposedly ended World War I, one of the provisions was the League of Nations-a beloved project of Woodrow Wilson's. It was decided that members of the league would be required to go to war against any nation that attacked another member nation. Congress refused to go along with such a plan. Why do you think Congress refused?

according to a group of U.S. Senators, the League infringed on the sovereignty of the United States. Some said that it might force the United States to send military forces overseas against its interests. According to the Constitution, all treaties must be ratified by the Senate.

Explanation:

Meaning that the treaty limited/undermined the authority of the US. Since the Senate did not approve the US could not sign because according to the Constitution all branches must approve.