How did America's entry into the First World War tilt the balance in favour of the Allies?

The entry of USA in the Great War placed huge resources, both in men and money at the disposal of the Allies. Britain, France and the United States launched a massive military offensive in July 1918. Subsequently, the Germans were pushed back and the German Emperor Kaiser Wilhelm abdicated the throne and fled to the Netherlands. Germany became a Republic and the new government signed the Armistice (An agreement to stop fighting) on 11th November, 1918 to mark their surrender to the Allies. Thus the Great War came to an end.