Not true. So much of the US, including many cities is uninhabitable or at least extremely inconvenient without a car due to a lack of planning that supports a car free lifestyle.
Also, while the majority of Americans live in urban areas, the rural population is not so small as to be insignificant.
The long term solution is to improve infrastructure and zoning laws to reduce the car centrism of the majority of the USA, this is already being done in many cities, but for the time being most Americans need a car.