Not at all, they were not the "end" of America, the election of JFK in 1960 doomed America, the future has no America in it, the name will remain for a long time, but America is gone, never to return.
The death of federalism under Lincoln, when these united States became the United States, and an illegal military action against the states, set into motion the forces that are destroying our country.
It was Nixon who implemented wage and price controls, established the EPA, OSHA, Clean Air Act, minimum tax, normalized relations with China, abandoned POWs and MIAs in Vietnam and was the first president to spent more on welfare than defense.
JFK, who was to the right of both Bush's, was just another milestone on the road.