I was ten years old and living in Tulsa, Oklahoma when Kennedy was assassinated. The next day, my Mom drove my sister and I to Houston, Texas to visit my Grandparents for Thanksgiving the following Thursday. I remember going through Dallas on US75, and seeing police cars everywhere. That was an eerie feeling.
A few years ago, my wife and I attended book signings and talks by retired Secret Service agent Clint Hill, the one who jumped on the back of the presidential limousine as it sped off. His talks (and books) were fascinating, but you couldn't help feeling sorry for Mr. Hill, as he lived these last 60 years with the feeling that he had failed in his job.
While not a Stephen King fan, I read his book "11/22/63". It's a good one and interesting for the time travel story, plus a glimpse into a future where Kennedy survived. Things don't turn out like you would expect (but I guess they never do in Stephen King land).
Tom is right, innocence ended and the world changed.