Pearl Harbor changed my life. In fact, without it I would never have been born.
My father was the son of a Missouri farmer living in St. Lewis when the attack happened. He enlisted the next day and volunteered to be a fighter pilot. In the US military, you had to be an officer to be a pilot so they sent the pilot volunteers to college for an intensive degree program. My father was sent to Macalester in Minnesota. While he was there he met my mother who was also a student there.
As the war progressed, the Army (The Air Force was still the Army Air Corps) decided that it had more pilots than it needed. My father's medical status was reevaluated according to new standards and he was transferred out of pilot training and sent to California to be trained as a radio operator and waist gunner. My mother accompanied him and they were married there.
My father survived the war without injury despite a close call when his plane was hit by anti-aircraft fire and had to ditch at an emergency air strip.
After the war, my father used the GI Bill to finish the degree he started in the military and to become a physician. He wanted to practice in a small city and saw an advertizement for Zanesville, Ohio in a medical journal. It was just what he was looking for and they moved there in 1952. I was born a couple of years later.
So, a chain of events that began with the bombing of Pearl Harbor led to my birth.
I am not unique in this. The entire Baby Boom generation is a result of the disruption of WWII that began with Pearl Harbor. The war and the GI Bill probably did more than any other event to change America from an agrarian nation to an urban one.
It is hard to say what the world would be like if the Japanese had not attacked 70 years ago. FDR wanted to enter the war against Hitler but most of the nation was strongly isolationist. Japan was the closer enemy but Hitler was the greater threat. If Japan had not attacked us when it did, we might have entered the war too late. We might have ended up with a Europe dominated by Germany and the USSR or even just the USSR.
Considering the alternatives, Japan might have done us a favor by forcing us into the war. Not that this excuses the attack. It was an act of incomprehensible savagery and because of Pearl Harbor, the US embraced the war instead of being dragged into it.