What impact did American entry have on the war?Missed it in class last week trying to make up a paper.

Word War I started in June-July 1914, and USA directly
entered the war nearly three years later by declaring war on Germany on on April 6,
1917. However even before U.S. help could reach the war fronts, the Allies had managed
to overcome the U-boat threat in the Atlantic.  In May 1917, Britain began to use a
convoy system, by which cargo ships went to sea in large groups escorted by warships
which was able to effectively neutralise effect of German U-boats. This improved their
position substantially.

The troops sent by the US to Europe
arrived in France in June 1917, and over a period about 2 million Americans served in
Europe. Thus manpower was the chief contribution of the United States to World War I.
This helped the allies to halt the string of successes of Germany on the western front
and then defeat them on all the fronts, forcing them to accept an armistice on November
11, 1918.