The Great Depression forced many nations to turn their attention inward in order to fix their economies.  This was especially true of the United States.  The United States never joined the League for fear of losing some of its own national sovereignty and a sense of disillusionment after the Versailles Treaty.  The worldwide depression ensured that the United States would not be a player on the world stage as it did not want to spend money on the military needed in order to ensure that nations played by the rules of the League of Nations.  The signatories to the pact, especially the victorious Allied powers of Europe, were too bloody from WWI to raise sufficient funds to equip soldiers needed to enforce the League.  Also, the Depression made more nations anxious to receive reparation funds from Germany—money Germany did not have due to the Depression and WWI.  This put a further strain on international relations and pushed Germany further into the arms of the Nazis who promised a stronger Germany and revenge on Germany's enemies.  While the League was failing before the Depression, the Depression really killed any chance it may have had to exist with or without American support.