Viewed from the present, I would say it's a function of falling living standards. As soon as workers had enough money to bolt to the suburbs after WWII, they did. Only from the standpoint of the oligarchy is forcing Americans back to 19th century wages and living standards an improvement in "efficiency." Think of the hourly productivity of a slave plantation: apart from a small fixed cost for a modicum of food, minimal clothing and housing, the cost of labor is nothing.
I would add clean water is readily available in rural areas via wells as is fire protection through self-organized volunteer fire companies. Medical resources are obviously scarcer, but you also get cleaner air, less crime, etc..
Given the size of the American market and natural resources available, there isn't any reason for housing and transportation to be so expensive except for the deliberate policies of the oligarchic managerial class in both government and business.
And yet I would contend that suburban migration in the post-WW2 period was only possible because the U.S. government had implemented two of the biggest pieces of socialist legislation in our country's history: the G.I. Bill and the Interstate Highway Act.
It's also worth noting that the post-WW2 period was an anomaly in that the U.S. was the only major industrial power in the world to emerge from the war with its industrial assets and infrastructure unscathed. As the rest of the world caught up to us over the next 20+ years, the U.S. lost a lot of its competitive edge in the industries that played such a big role in this suburban migration.