If you compare the early sixties with the late sixties, it is very clear that a radical change in culture occurred in an unbelievably short span of time. For all intents and purposes, 1962 was still indisputably a part of the "fifties", whereas everything after the Kennedy assassination changed America to the point that it was unrecognizable.
The Hit Parade went from Doo Wop hits, Elvis, Dion and the Belmonts, etc., to British Invasion bands like the Beatles and the Stones with a "grungier" or "psychedelic" sound.
Environmentalism came into being with such works as Silent Spring and The Population Bomb.
State-sanctioned race discrimination, despite no longer being in vogue by the late 1940s, was eliminated in this period through such legislation as the 1964 Civil Rights Act, the 1965 Voting Rights Act, the 1965 Immigration and Naturalization Act, etc. And by the end of this period, I would argue that overt racism in private interactions would have made one much more of a social pariah than in 1962, especially outside the South.
Feminism, which had long lain dormant after the attainment of suffrage, sprang back into being and was beginning to really shape public opinion by the 1970s.
The escalation of American involvement in Vietnam caused a deep cynicism and questioning of patriotism that arguably still shapes the nation's psyche today.
Basically, what happened? Are there other examples in history of the culture and every institution of a country changing in so short a time? Am I missing signs that radical change was already occurring in the background well before the 1960s? Why were the 1960s a time of such great change?
To some degree, the "Roaring 20s." Many young people moved to the city, away from their parents, young women began to get jobs in large numbers for the first time, they loosened their inhibitions with jazz, and the automobile (for some) made more sexuality possible (although most youths in those days only went as far as "heavy petting," that in itself was pretty revolutionary, considering the Victorian era previously). Women's fashions--shorter hair, shorter skirts--proclaimed young women's independence. On the "bad" side, Prohibition (a bad law that never should have been passed) gave rise to an era of heavy drinking, often of "rotgut" stuff (except for the wealthy, who could and did get the real stuff), and drunkenness. If it weren't illegal, people wouldn't have been so drawn to it. Still, unlike the '60s, the '20s youth were basically apolitical--they didn't get involved in "causes." At the end of the '20s, during the Depression, many single young people had to move back with their parents and contribute to the family, and thus the '20s era of rebelliousness and "flaming youth" came to an end.