The events that helped the United States decide to enter World War I were:
-GERMANY RESUMING UNRESTRICTED SUBMARINE WARFARE: In January 1917, the German government announced that it would carry out an indiscriminate campaign of submarine attacks thereafter. Again, Woodrow Wilson became enraged and on April 6, 1917, the United States Congress approved Wilson's request to declare war on Germany. The American participation in the war was slow at first, but the arrival in April of two million American troops changed the situation in favor of the allies, finally contributing to their victory in the war.
-THE LUSITANIA SINKING: The sinking of the RMS Lusitania, which occurred off the coast of Ireland on May 7, 1915 due to the attack of a German submarine, was one of the greatest naval disasters to have occurred to a line ship during the First World War.
The Lusitania was identified and torpedoed by a submarine U-boat U-20 and sank in 18 minutes, near the Cape of Old Head of Kinsale, killing 1,198 people and leaving 761 survivors. The sinking made public opinion in many countries opposed mainly to Germany, contributing to the United States' entry into the war, and became a symbol of military recruitment campaigns.
-THE ZIMMERMAN TELEGRAM'S INTERCEPTION: The Zimmermann Telegram was a telegram sent by Arthur Zimmermann, Minister of Foreign Affairs of the German Empire, on January 16, 1917 (during the First World War), to his ambassador to Mexico, Count Heinrich von Eckardt. In it the ambassador was instructed to bring to the Mexican government a proposal to form an alliance against the United States. It was intercepted by the British espionage services, and its content accelerated the entry of the United States into the war.
