Those who remind that there would have been just as many people to be butterflied into existence as there are people who would have got butterflied away. And who says there wouldn't be any Kennedy-esque and Bush-esque political families ITTL?
Yes, people will of course be butterflied in but they won't be Bush or Kennedy. You will have Bushes and Kennedys but they will be far different people then we know. Even Kennedy-esque and Bush-esque political families are almost certainly not going to be in TTL as the millions of things that are the historical background that made the Bushes and the Kennedys are not present.