Not disagreeing with the person above me here in the reply chain but wanted to tack onto the conversation that all of the following is historically true:

A) the lack of separation of means of travel has caused traffic issues for everyone involved as long as there have been more than one mode of travel (and those modes of travel weren't separated)

B) most people (but especially urban Americans) were opposed to cars and saw them as a blight on their city. The city was for the people, the road was for the people. This mentality is reflected in many many news articles which interviewed everyone from the average worker, to cops, to mayors.

C) that the car industry learned how to lobby against the American political system to take advantage of zoning laws and implement stricter guidelines for car centric designs such are minimum parking requirements.

Each of these things played a part in what American car infrastructure looks like today. People hated being afraid of cars, so local government was trying to separate cars from people. The car industry wanted the automobile to be the only form of transportation so it pressured the federal and state governments into passing laws which would result in this happening.

Wanted to highlight this because I feel like a lot of people think it was caused by one thing (namely GM), but life and history aren't that simple. It was a multitude of factors all overlapping with one another that were amplified by the lobbyists actions.