The correct answer to this open question is the following.
The United States decided to enter World War I because President Woodrow Wilson thought that Germany represented a real threat to the United States and other allied countries of the world. Two incidents made President Wilson ask Congress for a declaration of war. First, the interception of the Zimmerman telegraph in which Germany asked Mexico its support against the United States. The second, the sinking f the Lusitania ship.
When the US entered World War 1 on April 6, 1917, the US troops helped to move the Westward scenario and after two years, the Allied forces defeated Germany, the Austria-Hungary Empire, and the Ottoman Empire. Germany was forced to sign the terms of the Treaty of Versailles in Paris, France. The treaty did not reflect President Wilson's vision of "peace without victory" because Woodrow Wilson had envisioned a different peace treaty, based on his "14 Points Plan." However, European allies desired retribution mora than a peaceful agreement and wanted Germany to pay for all the destruction caused during the war.
