Around here, drivers are much more polite in Amish country, because as you say, they're used to going around kids and horses and buggies. Outside of areas with a large Amish (or horse-and-buggy Mennonite) population, forget about it.

I haven't ridden in the city in a long time, so my experience is small towns and rural areas. Between those two there's no discernible difference other than volume. You have rude, and you have clueless, and you have outright vicious. Precious few actually know how to ride around bicycles and exercise that knowledge.