Well, to answer your question, the reason why the automatic transmission was invented in America likely has to do with how American roads are generally built (especially in major cities), with lots of stop and go traffic because there's generally a stop sign or stop light at every block.
So even if Americans did end up driving manual cars for the most part, it's safe to say that newer roads would involve more roundabouts and less stop signs and traffic lights.
For example, if you look at countries where the majority of cars are manual, like England or Sweden, many have lots of roundabouts and fewer stop signs and stop lights, thus making driving manual much more convenient than in America, as there roads are generally less traffic congested. And poorer countries prefer manual transmission as the norm, since they usually have horrible roads, which the automatic transmission would stress itself. And that going steep while downhill requires being on 2nd gear for easy engine braking.