The great masses of the people will more easily fall victims to a big lie than to a small one. -Adolf Hitler
On March 3, 1917 Arthur Zimmerman announces the "Zimmerman Telegram" was a forgery made by British Intellegence Agents, widely believed by many Americans. Anti-British sentiment reaches new high's, and many people in America demand war. Past Anti-German propaganda, was now turned against the British. The sinking of the Lusitinia was now the United Kindoms fault because they had failed to protect it. The British continued to deny the Telegram being a fogery, to no avail, and desperatly pleaded with Mexico to reveal that the Telegram had indeed been sent by the Germans.
However, Mexico did no such thing. Mexico which was anti American and anti European felt that they would benefit if the America joined the war. That way more Europeans and Americans would die, and thus kill two birds with one stone. Mexico on the 28th of March revealed that the Telegram sent was about German trade interests in Mexico, and that the British did indeed forge the telegram.
On April the 3rd, President Wilson called for a joint session of Congress to decide wether or not wether they should declare war on the Enete. On April 8th, The House and Senate enthusiastically voted for a Declaration of War on Britain. Before the day was over, American troops were already crossing into Canada. America had entered the Great War.