Something often missed is that the US did not declare war on Germany on December 8. This created a dilemma for American policy and military planners who believed American involvement in WWII was inevitable and who viewed Germany as the greater threat. In fact, it had already been agreed that in the event of war with both Germany and Japan that 85% of America's resources would be devoted to defeating the Nazis. Hitler solved the American dilemma by declaring war on the US (for reasons that are still debated today) on December 11.
Over the decades there have been suggestions that FDR knew of the planned attack on Pearl Harbor and let it proceed in order to draw the US into WWII. I've read quite a lot about these accusations and believe them to be utterly without merit as do most historians who've reviewed the documents.
In 1941 was FDR seeking a way to get the US to intervene in the war? Yes, but it was on the side of Britain against Germany. War with Japan would interfere with that goal.
There have also been exhaustive studies of the intelligence (particularly via code-breaking) that the US had available to it in the weeks leading up to Pearl Harbor. During those last days, FDR and our military were tracking Japanese naval forces and believed an attack was imminent with the likely targets being the British and Dutch colonies in Southeast Asia and/or the Kingdom of Siam along with a lesser probability that American forces in the Philippines would be attacked. There were only very scattered references to Pearl Harbor amongst a blizzard of intelligence from the broken codes.
As is often the case I'll let Winston Churchill have the last word with his reaction to Pearl Harbor:
"No American will think it wrong of me if I proclaim that to have the United States at our side was to me the greatest joy . . . So we had won after all! . . . We should not be wiped out. Our history would not come to an end . . .I thought of a remark which Edward Grey had made to me more than thirty years before - that the United States is like 'a giant boiler. Once the fire is lighted under it there is no limit to the power it can generate'. Being saturated and satiated with emotion and sensation, I went to bed and slept the sleep of the saved and thankful."