What are some significant changes in American society that came about because of the automobile in the 1950s.
One significant change in the 1950s was the rise of the use of cars for entertainment by teens and young people. This was the age of going to drive-in movies and drive-in fast food places. It was the age of "cruising" in cars. Cars completely changed youth culture during this time.
Perhaps the most significant change that came about because of the automobile was suburbanization. Cars (and highways) allowed people to live relatively far from the cities in which they worked. This trend changed America from a country of cities to one of suburbs.
Adding: the Interstate Highway Act (1956) of the Eisenhower administration. which provided federal funds for the system of highways, ostensibly for defense purposes, promised "a quick drive to Grandma's house," but in fact allowed extended families to break apart.