[jcranmer]

A substantial fraction of the US's land area is locked up in Alaska, where there isn't "a road going through [the low-density] areas." What little long-distance infrastructure exists there is almost entirely driven by the existence of extractive industries (notably, but not exclusively, oil) that are lucrative enough to put in that infrastructure.

Rural Europe tends to be as lightly populated as, say, rural eastern US, not rural High Plains, let alone rural Alaska.