the only difference between the US and europe that really matters is the degree to which our identification with cars is ingrained, and therefore how that has shaped our development patterns. it's why we have so many large trucks and SUVs even though 75-95% of trips are single-occupancy, why we dedicate so much land to roads and parking, and why we care so little for public transporation, pollution, and transport/energy efficiency. it's not population density, inter-city distance, or patterns of demand, as these are also byproducts of the same phenomenon (cause & effect reversal).

That's not the only difference. People occupy way more space in the US.

For example, the population density of Paris is about 20 times that of Atlanta, a city ~3x as large (including the Greater Atlanta Area).

sure, and i'd posit that that's also a consequence of our love affair with cars. cars encourage urban sprawl (there's really no such thing as rural sprawl). perhaps a land value tax (with tax deferral until sale for non-wealthy primary home owners) can help us find an efficient optimum, something that would encourage urban density while not discouraging rural expanse.

>I’d posit that that’s also a consequence of our love affair with cars.

I’ve always operated under the assumption that there is massive selection bias in the United States for people who like more personal space. Never considered it was part of car culture.

the car, particularly for americans but also in other countries (mainland china being a prominently rising example), literally embodies individualistic expression, expansive freedom, and bold adventurism, as 50+ years of tv car ads can attest. that's not to pass an overly harsh judgement on any of those things, but rather, to say the balance is out of whack and has been for a while.

in LA, outside of a very few of the oldest core districts, even our supposedly sleepy neighborhood streets are often 40+ feet wide (note that cars are typically 6-7 feet wide), with 15 feet of public easement, and 15+ feet of mandatory setbacks, so urban land use gets out of whack real quicklike that way.

That's partly consequence rather than cause. All that space is being taken up by parking lots and wide streets for on-street parking.

Don’t forget the extremely large us air network!

that doesn't matter either. air networks in both the US and europe are plenty extensive.

and to be clear, it's not that high-speed rail is an unmitigated good, but that we love our cars so much that any challenge to their supremacy is a literal (perceived) threat to our own egos.

high-speed rail makes a ton of sense for the coastal cooridors, as well as at least a few interior ones (e.g., the midwest, texas). it's probably not a good use of resources for a cross-continental passenger run of HSR, since air can more efficiently and flexibly link the coastal and interior intercity networks.