When you say "separate ... dealership franchises", are you counting each physical location once, or once per brand? Around here, many dealerships carry multiple brands. Also, there tend to be multiple dealerships clustered together (probably due to zoning, and tax incentives that some municipalities offer), so they're not as smoothly distributed as McDonalds. Still, those are amazing numbers!
To be honest I just took the numbers from http://wiki.answers.com/Q/How_many_car_dealerships_are_in_Am... which claims to quote the National Automobile Dealers Association. More completely that page says "more than 17,000 new car and truck dealers with approximately 37,500 separate franchises" so even without the 'separate franchises' the number is still higher.
