I'm with jno on this one. Since I live in the U.S., I've never participated in such tours, but the ones I see have an awful lot of blue-haired matronly passengers. I suppose it depends on the clientele for whom the operator aims. Biggest problem is the adherence to a schedule over which one has no control. You might wish to get up at the crack of dawn or you might wish to sleep in for a while, neither of which is an option on guided tours.
I well understand how foreign travellers are concerned about driving here... heck, some people that live here don't like to drive. But there are so many side trips one can take out west, where I live, that it would be a shame to miss them for the sake of a set-in-concrete itinerary, and the driving is simple, coming from a resident, of course. But at any rate, welcome to the U.S.!