There are definitely uncontrolled intersections once you get out of the cities. My understanding is that if unmarked, there’s an implied give-way at the side road in a T-junction and all roads in a four-way junction.

I imagine self driving cars won't be outside of cities for years and years.

Outside of cities on limited access highways seem like the much easier situation--and, frankly, a pretty significant win for both comfort and safety once people give up their dream of having a personal chauffeur for their entire lives. It's self-driving in e.g. Manhattan or Boston that I can't really begin to imagine in less than decades.

Also people regularly just ignore the lane markings (and break all the other rules too...). You have to consider all those cases as well.