What convinced many Americans that the united States needed to prepare to enter the world war 2?

Many Americans were convinced of the need to prepare for World War II due to a combination of factors, including the aggressive expansion of Axis powers like Nazi Germany and Imperial Japan, as evidenced by events such as the invasion of Poland and the attack on Pearl Harbor. Additionally, the failure of isolationist policies and the increasing threat to global democracy highlighted the urgency of military readiness. Propaganda, such as the "Four Freedoms" speech by Franklin D. Roosevelt, also played a crucial role in rallying public support for involvement. Ultimately, the attack on Pearl Harbor on December 7, 1941, served as a catalyst that unified public opinion in favor of entering the war.