Answer:
It convinced Congress to carry out war against Germany and Japan which were both part of the Axis.
Step-by-step explanation:
Franklin Delano Roosevelt was willing to join the fight in Europe against Hitler and had Churchill that he would be on their side in case a conflict triggered.
The Congress was still reluctant to have the USA take part in WWII. At that time Conservatives were isolationists.
After WWI, the USA withdrew from the international sphere and returned to Isolationism in the twenties and the thirties. The Pearl Harbor attack would force the nation out of its isolation and compel it to intervene internationally.