The correct answer to this open question is the following.
Wilson's support for the League of Nations stood in the way of Senate support for the Treaty of Versailles because the Senate supported the isolationist US after the war, and entering the League of Nations meant the opposite. It meant again to be involved in foreign policy dealing with the issues of other countries.
US President Woodrow Wilson had created a "14 Points" to bring peace to Europe and avoid another world war. His ideas established the foundation of the League of Nations, but in the end, the Senate of the United States did not support the idea of the US to be included in that international organization.
President Woodrow Wilson personally negotiated the treaty following World War I, promoting his vision for a system of collective security enforced by a League of Nations. When the treaty arrived in the Senate in July, Democrats mostly supported the treaty, but Republicans were divided.
