The attack on Pearl Harbor made many American people believe that war was necessary.
Step-by-step explanation:
Some people before the attack on Pearl Harbor were isolationists and were that way since the end of World War I. Isolationists believed that their country should essentially stay out of foreign problems, as a war might start. World War I took a huge toll on the United States as a whole and many people did not want a repeat of it.
With the attack on Pearl Harbor, this isolationist attitude started to change. Many people started to believe that war was needed in order to stop Japan and even wanted to avenge the lives lost in the attack. Fear and anger spread through the country, along with a newfound patriotism.
President Franklin D. Roosevelt asked Congress to declare war on Japan and they very quickly agreed. Most people agreed with this decision after what happened at Pearl Harbor.