It simply must be said. A major (or even the main) reason that american city planning is so atrociously bad, and continues to be that way, has a everything to do with racism in America. Cities do not want easy transit to all parts of the city, because the city is designed with the intention of keeping white people separated from black people. This exists not only in the lack of decent public transit, but also to the dominant form of transit in the USA: the car. Setting aside the fact that cutting up a city with highways is always a poor design choice that worsens life for everyone in the city, you may notice that these borderline impossible to traverse, noise machine, air quality killing, auto insurance payout generating death trap roads tend to conveniently isolate the portions of the city where everyone except fairly well off white people live, thereby not only making the city environment significantly worse in general, but also actively preventing any sort of integration of various communities in a way that is uniquely difficult to work around.

As if that wasn't enough of a clue, the often scarce public transportation itself can serve as a further means of isolation, by acting not as a dedicated transit network for inhabitants of the city to wherever they wish to go, but a means of transporting poor minority workers to and from work, completely out of sight of the white upper class, who often wouldn't be caught dead on public transit. This particular failure of design isn't necessarily racist, it's a nearly universal trait of American public transit that has to do with the fact these systems were designed exclusively with the idea of transporting poor people who can't afford cars to work, and not to facilitate movement across the city no matter the destination. This is why american cities often have fairly minimal train systems with immense rail line transfer hubs near where the majority of non-car owning commuters work: they're optimized for capitalism, not convenience.