The treaty of Versailles was one of the most unfair treaties in history. It was forced onto the German by the Allies after the war. The Allies said that Germany was at fault in the war and that they had to comply with the Treaty or else they would be attacked again. Germany had no choice but to comply with them because they could not handle another attack against them, no matter how much this treaty damaged their confidence and nationalism.
The treaty said that the Germans had to pay for all of the reparations from the war. It also said that Germany had to accept the fact that the war was their fault. This was a huge insult to the Germans. It meant that the Germans would have a dent in their nationalism because they were not going to be able to do anything for their country for a while because the reparations were so much money. They had to pay for everything, not only their reparations, which was more than enough, but they had to pay for Britains, and all of the Allies and much more of the war reparations, and since they had such a strong sense of nationalism, this was a huge blow to their pride.
The Germans would get very mad at the Allies because of this. Only bad things came from it. Eventually the Germans got powerful enough to the point where Hitler decided to carry out the plans of Germany in the first World War.
http://www.spartacus.schoolnet.co.uk/FWWversailles.htm
The US played a major role in the War, the only thing is that they were not in the war for a while. At first the US was neutral because they did not want to get into war. They were neutral because Woodrow Wilson promised the US that he would not go to war if he was re-elected, and the US then re-elected him. The US didnt go to war, for a while, but eventually they did. The main reason that the US went into the war was because German U-boats sank the Lusitania. The US decided to get into the war because the seas were not safe, and they wanted to end the war as quickly as possible because they thought the seas should be free.
The US then joined the war. They joined it very mad at the Germans so they decided to join the Allies. The Lusitania was a British cargo and passenger ship. It was sank by German torpedoes. The Lusitania was considered a floating palace and was thought of as one of the best boats on the sea. People thought that the Lusitania was unsinkable because of its speed, but they did not know how fast the German U-boats were in the first place. It was hit by two different waves of torpedoes. The first wave did not sink the Lusitania, but it made big enough holes in the boat for massive amounts of water to flood into it. It is said that they could have been hit a second or third time, but the second explosion was the most harmful, and many believe that it was not caused by a German torpedoe, but by an explosion inside the ship. Because the Germans decided to sink the Lusitani, the US entered the war and played a huge role in the defeat of Germany.
http://campus.northpark.edu/history/WebChron/USA/Lusitania.html