How good are American roads?

> Interestingly, I expected cold places to have lower road quality in general due to things like freeze-thaw cycles and the impact of road salting, but there doesn’t seem to be much correlation. Plenty of cold places (North Dakota, Wyoming, Minnesota) have good-quality roads

Not sure about those states in particular, but I have anecdotally noticed that some of the places with the harshest winters do some of the least road salting -- because salt is mostly usable for light to moderate snowfall and the people who live in the harshest climates are often better equipped to drive on hard packed snow.

The more obvious reason is that colder places do not get as many freeze-thaw cycles. It simply stays frozen for a few months. In contrast, much of the northeast experiences many more freeze-thaw cycles since even in the winter it is warm enough to thaw the ice on some days.