Even Franco and Salazar couldn't hold back free love and rock and roll, despite having cultural policies only slightly removed from the Taliban.
The US had rock and roll. And therefore, the world did.
The US had a flourishing drug culture. And therefore, the world did.
The US was the first country to have birth control pills. But soon after, the whole world had a sexual revolution.
I could go on and on. I don't think this was all a "group phenomenon" as much as I think the US led many nations down a single slippery slope.