I don't know if they are available in the States but I have seen one in New York and I have taken pictures already. Image Unavailable, Please Login Image Unavailable, Please Login
If you have never been a passenger in a car with a professional track driver I can tell you it is quite an experience. It is even more intense when its your own car being pushed to the limits.
ive riden with some of the best drivers AMG has to offer. Its a different experience. Also, its a different experience from the pass seat. Also, when you are driving you know whats coming based on your inputs, also of the experience comes from you not knowing what is exactly going to happen. but to answer your question, yes i have ridden with some great drivers. Would I pay for it? No.