Basically, JFK changed the socio-political narrative for the country and most likely led to the current polarization of the country by advocating for an activist, positive vision of government that inspired liberals even though he was at best an Obama-like cautious centrist on domestic policy. But he changed the dialogue during the coming of age of the Boomers and the decades since were forever changed as a result.
My parents were both 2nd generation Irish Catholics from Massachusetts, the children of poor, working class immigrants. So the assassination of President Kennedy was as profoundly dismaying as his election three years earlier was a cause for joy. When he announced the creation of the Peace Corps, I was 11 years old and knew little about the world and yet I decided that I would be a Peace Corps Volunteer someday. He was that inspiring to a kid from my background. I did become a PCV and spent two years in Ethiopia, which then changed the trajectory of my life and career.
I was in my 8th grade class at St. Philomena’s primary school in Pittsburgh when one of the nuns rushed in and whispered to our nun and we were ordered to the small school hall whereupon a TV was rolled into the hall and Walter Cronkite and CBS was turned on. The whole thing was totally surreal; none of us really understood what was going on and the youngest kids were lost. When his death was confirmed we were sent home.
Two days later and television was all about the assassination all the time, I was in the basement watching the transfer of Oswald to the county jail when Oswald was shot live on TV. This was probably the first live murder on television,i.e. in real time. Certainly it must be one of only few. I remember it vividly and remember being stunned and not really comprehending what was happening, heightened by the immediate pandemonium in that very crowded basement area. I ran up and told my Mom what had happened.
Well, the conventional wisdom is that JFK’s assassination enabled the passage of civil rights and possibly voting rights legislation as well as the War on Poverty and maybe other liberal legislation. His tax cut is also widely cited as the precedent for Ronnie Rayguns radical tax cutting (not good given a different fiscal environment).