I never thought of Cars as being an appeal to Nascar. I thought of it as being essentially the same as the opening sequences to Toy Story, where the toys are living out the fantasy world of the kid.
To me, the whole movie (and I would guess Cars 2, which I have not seen yet) seemed more like the kind of adventure you have with toy cars on your floor and Hotwheels track than an actual world populated by Cars. It's about living out those childhood fantasy adventures, not "what if everything were cars?"