Use the excerpt below to answer the question. When I addressed the Congress on the twenty-sixth of February last I thought that it would suffice to assert our neutral rights with arms, our right to use the seas against unlawful interference, our right to keep our people safe against unlawful violence. But armed neutrality it now appears, is impracticable. -President Woodrow Wilson's Joint Address to Congress, 1917 Which factor contributed most to the policy change described in this excerpt? the possibility of an invasion of U.S. territory the German use of unrestricted submarine warfare the success of the U.S. isolationist position the German use of naval blockades