Level 5 is the level that matches human skill, but level 4 is the level that actually matters economically, because it's the level at which it's safe for the human to stop paying attention to the road, freeing up their time for other activities. (Let's say on average it must require the human take over no more than once an hour. And I'll allow it if they're only level 4 on a clear summer day.)

"Available" means I can either purchase one myself, or rent one. Long wait times are acceptable in rural areas; presumably renting one would cause it to drive itself out from the nearest major city, arriving a few hours later. There's no price cap, but it has to be a commercial product; it can't be a prototype that someone will let me borrow if I pay them $1 million.

This is about both technology and regulations, so if they're banned this resolves NO. Let's say that to resolve YES, I would need to be able to use the car to get from any normally-driving-accessible point in the continental US to any other such point with <3 hours of my own time spent driving and no more than a 50% increase in total trip time, with the exception that I'll allow total bans in up to 5 states. This means that if there are a few dozen cities that ban the cars that's fine, but if they're banned on all interstates or something like that, that's not sufficient.