To add one thing to the mix (as there are so many aspects to all this, and I see where so many posters have nicely hashed them out)...

With WW2 and then the initial years of the Cold War, and the nature of these situations, a lot of society really started looking up to the generals, the politicians, the media, etc., for guidance. There arose a kind of trust in the 'elites' that hadn't really previously been a part of American culture or society. It went hand-in-hand with people wanting to just put everything on auto-pilot. They were worn out by years and years of Depression and then War, and then the fears of the atom-bomb. People 'checked-out,' and left everything to those they deemed experts, from Dr. Spock to Walter Cronkite. They basically handed over their authority to a lot of northeastern liberal elites, who dictated all trends from art to media to government. In essence, they handed their kids' brains over to them.

With the addition of technology, advertising and the business world helping to cultivate a whole new 'teen' consumer class, which was a new, separate entity, it drilled into the growing baby-boomer generation a sense of self-importance and specialness. Which gradually began defining itself as a rebellious opposite to everything before it. Stoked by the usual commie anti-American types. And this pretty much led to the hippies, and ripped up the fabric that used to keep the society strong, and had contributed to positive, moral civilizational growth.

In shorthand, yeah, I blame the hippies. But in the wider scope, as I described above, it was baked in the cake. The country basically went off the rails rather quickly following WW2, as it handed over all authority to lefty pie-in-sky intellectuals and elites. Normal folks had maybe a decade or two of easy-going life, fairly oblivious, and living with blinders on, while all that rot was taking hold, finally to explode in their faces by the 1960s.