As war consumed Europe, Americans hoped that the Atlantic ocean was enough to seperate them from it and keep them out of the war.
President Wilson said that the US would stay out of it saying it was "a war in which we had nothing to do".
But America could not help but take sides. As immigrants from Europe gave roots to many Americans, it was hard for them not to be opinionated about which side to take. The herirage shared by most Americans and Britain put American public opinion on the sides of the Allies. Trade between the US and the Central Powers also shrank giving another reason it was hard to remain neutral. Adding to that was the fact that exports to the Allies nearly quadrupled and ties between them became closer.
In 1915 the British passenger liner, the Lusitania was sunk supposedly by German U-Boats, pissing many people off.
Most Americans considered this grounds for war. Wilson, however, refused to take extreme measures against Germany but instead sent them several messages insisting that it's government safegaurd the lives of noncombatants in the warzone. When the Sussex was torpedoed by a German torpedo Wilson demanded that they give up submarine warfare or risk war with the US. The Sussex pledge was made out of that where Germans said they wouldn't sink any more merchant ships without warning.
Wilson was re-ellected in 1916 and focused on finding a peaceful solution to the war. He knew the only way to keep America out of this war was to end it altogether.
Germany announecd on January 31st, 1917, that any vessels in the waters near G.B., France, and Italy would be sunk without warning. This was a violation of the Sussex Pledge and caused the US to break off diplomatic ties...