I can't speak for the US, but in Europe (experiences from Sweden, Norway, Russia) rural areas usually have a handful of taxi drivers and you "use their services" by calling their numbers which you can get from locals.
In Finland we had a law that required the taxi monopoly to provide services even in rural areas, so disabled and elderly people could get transportation to services they need. Worked well in my town of 7 000 people except sometimes on weeknights the only driver could be in the next city 50km away.
(Had, as in they changed the law few years back. Not sure how it's now)
Robotaxi(s) could be quite good solution to the problem - the drivers were often pissed if you called them for a single ride when they were home or far away.
