I just drove across ten US states and five Canadian provinces from the West to East Coast, shipped my Jeep to Europe by way of Iceland, then drove 100 miles through Denmark, Germany and Switzerland.

Driving on the freeways in those mainland European countries was immensely relaxing and easy - the road quality is vastly, vastly better than the US or Canada. Expansion gaps, cracks and imperfections are almost imperceptible.

Anecdotal, of course.

I have a strong memory of Driving I-40 from Cali into Arizona and not being able to maintain 60mph because the potholes were so big I though I was going to break the suspension on my Jeep.

I think anecdotal evidence may be a reasonable proxy for those countries, although at least in stereotype and anecdotally they are very far from representative of (even) western Europe. I've noticed quite a bit of variance between major highways and smaller highways or other roads across Italy, for example.