I don't remember Kennedy from when I was a kid, however I did a little research years ago. From that, I remembered Connally and his wife. The magic bullet made him hard to forget. It was a 6-seater no doubt about that. My answer would be at the least, 5.
Don't remember about CP30.
Jif PB no doubt. I was a young mom in the 80's and remember that slogan, "Choosy Moms choose Jif."
I think Mandela Effect was made possible via internet/TV. Think of the enormous amount of data! Collectively we drive products, advertising, you name it, by purchase and adding content to the net. Even politicians tailor their ads to appear to give the people what they want, from analyzing data collected off the web forums.
The reason it's called Mandela Effect, to me is a great indicator of how the dominos got set up to begin with. Just my .02.