***What really changed America, in my opinion, began with the Vietnam War.***
It started with the beatnik movement and then the hippie movement as the bulk of the baby boomers began to challenge all authority for anything. Sex, Drugs, Rock and Roll! Tune in, Turn on, drop out!
Maybe. Those first generation beats like Kerouac and Ginsberg grew up in the Depression when there really wasn't much work and people were jumping on to freight cars or loading all their belongings on to a truck and setting off. I wonder if they weren't trying to prolong that restless, nomadic period.
The second generation beatniks and hippies were children of postwar affluence which they thought would never end. There's a tradition of rebels against adulthood and adult responsibilities going back to the Lost Generation of the 1920s, the Greenwich Village bohemians of the 1910s. Maybe you could trace that back to the Transcendentalists of the 19th century. As the country grew richer more people thought they could afford such a lifestyle.