Democracy in the US did not die with JFK. The hopes and dreams of progress were taken up by his Vice President, LBJ as he immediately started work on his Great Society.
He passed the Civil Rights Act (1964),?the Economic Opportunity Act (1964) the Voting Rights Act (1965) and created Medicare/Medicaid (1965)…and the 25th amendment got passed outlining what happens when a President dies in office 1967).
Democracy survived the backdrop of 60’s political assassinations and war.