The 1960s was when the US got welfare and SSI (disability insurance for people who haven't already paid into the Social Security system).

Being able to rely on these governmental benefits might have made families less reliant on the local community, churches and extended family, which in turn might have caused daily life to feel more alienating or atomized.

I bring this up because welfare and SSI can be viewed as a move towards collectivism and away from individualism, so arguing about how individualistic the US has been over time is kind of a sterile game because the answer is highly dependent on the exact definition of individualism.