When World War 1 broke out in 1914, the United States attempted to remain neutral and was a strong advocate the neutral rights of nations. The U.S. liked to believe that the war was strictly a European conflict, but they would soon understand that they were inadvertently part of the war effort and entering war was inevitable. The U.S. was never truly neutral in the first place, but in fact supporting Europe the whole time. The reasons for breaking neutrality were more political and economical. It was the United State's best interest to abandon its neutrality, and choose to go to war on the side of the allies for the future protection of American assets and welfare.
The U.S. supplied the Allies financially and was afraid that if the Allies lost the war, their debts would not be paid. America has to make sure that it was still able to collect loans from Britain and be able to help out the French government by also giving them loans. Also the abrupt increase of the amount of exports for the Allies and hasty decrease to Germany was a clear sign of favoritism. For a neutral nation to have so much economic influence over belligerent nations was a clearly biased in favor of Britain and France (document 1 & 2). The U.S. was clearly profiting the most from the war though they were neutral. These acts of discrimination exposed the faults of capitalism and farther fueled the communist cause against capitalism as pointed out in Document 3. .
Then there was the Zimmermann Note, which revealed the German plot to ally with Mexico in the event that the United States the entered the war. Though the note was simply a contingency plan if U.S. were to enter the war, nevertheless it would pose a direct threat to the United States. The note was intercepted by British intelligence and created a public uproar that demanded that U.S. direct involvement into the war. The public played a great role in U.S. entry in to WW1. Also, British propaganda brain-washed the public through exaggerated stories of Germany atrocities trying to rile up the nation.