A leader was absolutely imperative.
The West won the war and seriously lost the peace.
The Treaty of Versailles was negotiated while the Racist Woodrow was recovering from the Influenza pandemic, which probably caused the stroke, and that treaty was crushingly harsh on Germany, which led to the rise of Hitler and the Second World War.
The Racist Woodrow wasn't there to lead the crusade for the League of Nations in the US and the Senate rejected the idea. The League without the US leadership proved to be even more useless than today's UN.