It was a conscious decision. After the Second World War, the US needed somewhere to shift all of the manufacturing that had been built for the war effort. So cities were deliberately designed to keep houses away from jobs away from shops, so you need a car to get around, inducing a market for the personal car that never should have existed. People forget that before the car, there were cities across America that were walkable and had streetcars. The current state of affairs was never preordained. It’s the result of decades of corporate influence over government decision making.