I think it'll be more like "Autonomous driving is required on all roads that are in the system." America has so many roads that it's completely unlikely to think they will all be covered, especially back country roads and dirt paths. What I suspect would happen in that case is the car will drive you as close as it can, stop and idle, then give you an audio and visual reminder that YOU are libel for anything that happens beyond this point and an agreement you need to okay... with perhaps an option to buy insurance for this trip off the system....until self-driving cars become mandated, yes. Much like seat belt use, I see self-driving cars as the sort of thing where there will be a tipping point beyond which Government will up and say, "Welp, they're safe enough, so now everyone has to have one. Autonomous driving will become illegal after 2xxx."
The ability for cars to drive independently is simply too basic and necessary to completely remove. Its likely that learning HOW to drive will still be required to access this feature though, or at least necessary to do it legally.