I've driven the roads of most U.S. states -- and I'll be driving more of 'em this time next month, up in the northeast. I've ridden many of them in the south on a motorcycle, too. I've driven in a number of foreign countries, too: much of western Europe (including the U.K.) and select places in Central and South America, as well.
Each time, I note things like pavement quality, general driving/traffic habits, general vehicle condition, etc. almost by osmosis.
Some observations:
- In general, road quality is dictated by state funding -- even stretches of state highway that go through federally-owned land such as National Forests. Nowhere is this more evident than on the Cherohala Skyway in the Smoky Mountains. The pavement is phenomenal on the North Carolina side -- and right at the state line with Tennessee, it changes drastically for the worse. That stretch is within the Nantahala National Forest -- but it's a state highway.
- U.S. Highway condition also varies state by state -- but since it's largely federally funded, condition is as much a political 'porkbarrel' issue as anything. For example: Before Bill Clinton because President, Arkansas' highways were atrocious. Within 2-3 years after he took office, the state had some of the country's best roads.
- The farther north one goes, the more funding roads need to be kept in good condition. Why? Freezes. In Texas, we rarely have to worry about snow, much less frozen ground, salt, melt-off erosion, etc. Yet the density of roads in the north (at least in the U.S.) is higher than in the south in most cases ... and, in general, population and economic growth is higher in the South than in the North. Those factors, among several others, are largely why Michigan, Massachusetts, Ohio, etc. are frequently on the worst-roads list: Those states have far bigger issues than road condition to address ...
- Internationally, roads fit the transportation culture. Germany's known for its Autobahn primarily because it was conceived and built during a time when roads were primarily thought of as individual transportation lanes, while things like rail and ship were commercial and/or military -- or blown to bits because of WWII. In Eastern Europe, roads are also individual but primarily serve focused locales and small commercial endeavors such as farming -- much like a lot of the western U.S. before WWII. Only countries with a reason to have highways between regional economic centers have them, and density varies depending on a country's level of urbanization and post-industrial development: England and Germany have tons, while Sweden and Russia have few.
Anyway ...
Best roads in the U.S. - Arizona
Worst roads in the U.S. - New York (this may change after my trip, LOL)
Best roads in Europe: Italy
Worst roads in Europe: Britain, anywhere in the Balkan peninsula
All of that pales in comparison to the roads in Panama and Ecuador. I wouldn't own a late-model car of any make or model in either of those countries.