How did the USA contribute to the Allied war effort?

On April 6, 1917, the USA declared war on Germany. The US were essential to the allied war effort and were significant contributors. 

Firstly, the US organised anti-German campaigns. Through these campaigns, huge sums of money were raised by taxes collected from the American Public. This supply of money was used to manufacture and trade weapons and ammunition for the war effort. 

Secondly, the US navy was able to defeat German U-Boats in the Atlantic. This successfully created a vital safe transport route for food and material supply which was desperately needed in France and Britain. It also reduced the number of U-Boats that could attack the British crossing the Channel into France.

Thirdly, over 2 million Americans crossed the Atlantic to land in France. At their time of arrival, Germany was struggling to replace its troops, so the US war effort was short and successful due to the large influx of soldiers.

Finally, even before they had joined the war, the US provided the Allies with loans that were to be paid back with interest after the war. Not only did this benefit the USA, but it also helped the Allies to trade weapons, material and food desperately needed for the war effort and to repair damage caused by the axis powers.