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.
(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.