Answer:
What changed is that United States were attacked by Japan without previously being warned, so this was a turning point for everyone. American territory was under attack and there was no other solution than to include the States in war.
Step-by-step explanation:
Attack on Pearl Harbor, United States harbor on Hawaii is one of turning points in the war. United States who were neutral until that moment were provoked by Japanese who left them no choice. United States joined the Allies. People supported this decision as everyone was furious because of the attack.