OTL, despite it being the most commonly cited reason for american entry, America didn't get involved in the Great War until over a year later with the zimmerman telegram. But say that there were no weapons on the boat and more americans died, and american outrage was far stronger than otl. America declares war on the Kaiserreich on June 1st, 1915, as Woodrow Wilson is rendered unable to suppress the fury of the american people. What happens?
Actually, it was
two years later, and it was Germany's decision in favor of unlimited submarine warfare (including killing Americans
on American ships) more than the Zimmerman telegram. that was responsible for the US entering the War. (And of course there were other things that happened between the Lusitania sinking and the 1917 decision for unlimited submarine warfare that soured public opinion of Germany, such as additional sinkings, the exposure of German espionage in the US, etc.) But as outraged as most Americans were about the Lusitania, it would have been very difficult for Wilson (or another president) to have gotten a declaration of war at that time, even if he had wanted one. As Arthur S. Link writes in
Woodrow Wilson and the Progressive Era, 1910-1917, pp. 164-166:
"Americans were shocked and horrified at what they considered the deliberate murder of almost twelve hundred noncombatants, including 128 Americans, on the high seas, by direct order of the German government. But except for a small group of ardent nationalists headed by Theodore Roosevelt, few Americans wanted to go to war to avenge the wrong. The great majority applauded when Wilson acted deliberately during the crisis, even when he declared in a speech at Philadelphia on May 10 that "There is such a thing as a man being too proud to fight." 4S From governors, senators, congressmen, and other spokesmen came fervid appeals for peace. From Senator Thomas S. Martin and Representative Hal D. Flood, two powerful Democratic leaders, came an explicit warning that the country did not want war and that the President might find it impossible to obtain a war resolution from Congress.
"It should not, however, be assumed that in the subsequent negotiations with the German government Wilson's strong arm was paralyzed by popular and Congressional opposition to a belligerent policy. The president was confident there would be no real diplomatic crisis and, in ny event, contemplated no stronger step than severing relations with Germany..."
https://archive.org/details/woodrowwilsonand007665mbp/page/n207/mode/2up
