As an American business owner with two kids, not only is "a" car needed, we actually need two. I don't see this changing for other Americans, unless you live in the city.
I live about 1.5 hours from Boston, in a small town less than 10K residents. While I could bike or walk to work I could not manage our busy schedule with one car, let alone no cars. Also, one of my cars is a truck, which we use to pull a large travel trailer when we travel (among other truck things). To my knowledge, that simply isn't an option for ride-sharing and rentals.