Overall i would say that the average American car driver is quite a good driver. Hands down no question, the worst drivers in terms of quality are California driver's. True I've only been to like half the states now but they are, to my eye, been exceptionally shit. Pickup drivers tend to be the bmw shitbox drivers of home. Aggressive, offended if you dare pass them, etc.
Traffic signage is terrible, I've seen a lot of just ought right wrong signage, both temporary and permanent ones. Vegas is def the worst offender with just having no functional signage and what exists tends to be wrong.
Highway qualities and connectivities are top tier. With a car, you can go anywhere. With legs, you can die under a car in a lot of places.