As someone who lives in Houston, the simple reason there is sprawl is because its flat and land is cheap. This makes it easy to live on large lots or on small average. It's also hot, so people spend more time indoors and drive everywhere.
I'm glad someone said this. The size of the interchange vs a small town in Italy is an odd comparison. Land and gas are cheap in one place and they're not in another. That's basically the end of the story.
I think a lot of these country to country comparisons bank off the fact that people presume they're dealing with an oranges to oranges comparison like two sporting teams or something equally sized. Evaluating two comparands on some single concept they both happen share in common without looking to the specifics is grossly inadequate.
Concepts like city, country, state, hospital system, etc, can indeed both be shared between two countries at a conceptual level. However those concepts can take drastically different forms with their reality on the ground. The two comparands' actualizations of these concepts can be huge simply looking at scale alone. As far as I can tell the US dwarfs pretty much any EU country in terms of population, land mass/area, and a bunch of other stuff too I'd imagine.
I'm awakening more to the fact that without highlighting from the outset any known differences in scale one can be lead to strange conclusions in the results of comparison. There's that common software architecture analogy regarding the techniques to build a single family detached house being woefully inadequate at building a skyscraper.
It would be nice to have some normalized terminology of city and country etc that speaks more directly to the population scale at hand.