The Twentieth Century was a very different century from the previous times. There was massive growth and advancement of the human race but also there was brutality displayed by humans that was never before seen. Major advances in technology, science, health were made and people started to live longer lives. American also experienced major declines, as in the great depression and growth to having half of the world's wealth.
During Woodrow Wilsons presidency world war one had occurred and at first America wanted to stay out of it. During the early 20th century America considered that affairs that happen in Europe don't affect America in any major way. The US had made a declaration of neutrality in 1914 and would not support either side of WWI. Even though Wilson had stated to the public that America was not helping either side he was secretly supplying the British with arm, and even after the Germans sunk the RMS Lusitania which had US citizines on board, he still maintained nutralutlity. The ship exploded due to the fact that the hull of the ship was loaded with explosives that were being shipped to England, and the Germans knew that they were there. Even though Germany declared unrestricted submarine warfare and that threatened the commercial shipping of the United States Wilson still tried to stay neautral.
There was a turn for events in WWI when Germany tried to enlist Mexico to fight the US. When the President learned of the Zimmermann telegram he took America into World War I. Wilson had decided that Germany had become a real threat to the United States. Wilson statement announcing a "war to end war" meant that he wanted to build a basis for peace that would prevent future catastrophic wars and needless death and destruction. There has never been a war to end wars before and this new kind of war was meant to be a good thing, to stop the bad guy from killing innocent people. People were very excited and optimistic for the war and there was great applause from congress and during his war message.
When American troops arrived to Europe it was nothing that they have imagined it to be. There was massive killings and the brutality was unheard of. Toward the end of the war Wilson proposed the Legue of Nations "Fourteen Points" to join nations and to end all great wars. The fourteen points was meet with great opposition from with in the us government, because lots of politicians did not want to make any long standing aggrement with other nations. Some of the points were the removal, of all economic barriers and the establishment of equality of trade conditions among all the nations consenting to the peace and associating themselves for its maintenance and absolute freedom of navigation upon the seas, outside territorial waters.