The dismantling of public transit in the US started in the 20’s, not the 50’s. GM, other auto and truck manufacturers, and the oil industry began buying up street car and train companies through proxies and then shutting them down. They also used government influence to make them unprofitable.
A former head of GM was made transportation secretary in 1948 and used the department of defense budget to build the highway system, further damaging any chance public transit had of taking hold here.
By the late 50’s we had all but destroyed any hope of having a mixed transit system.
The US wasn’t built by public transit though, it was built by car and truck. Public transit in the post industrial era has always been a pipe dream on the periphery for Americans.
Manifest destiny’s “go west, young man” has morphed into “go into debt, purchase cars and houses, young man.” And like “pulling yourself up by your bootstraps” it has always been a lie.
With the legalized bribery system known as lobbying in this country we never had a chance at being anything but a facade of democracy propped up by corporate avarice.