Without really reading the article, I think maybe the parent's point is that the US basically pays for large portions of defense and security of Europe, especially when it comes to the need for blue water navies to protect trade. That frees up a lot of time, money, and manpower for them to spend on not defense, and spend instead on infrastructure and nice things. It's also nice that another effect Pax Americana has contributed to is that the majority of Europe has stopped starting progress-destroying wars with each other every two decades.
The US doesn't get that benefit as the self-employed enforcer, and I'm sure we're all aware of how insanely massive the defense budget is.
So the argument is actually that the US can't have livable cities because they spend all that money defending Europe? Because of the implicit assumption that European-style cities are more expensive in upkeep than current US cities?
I think the assumption is more that us Europeans can afford such decadent, livable cities because we don’t need to spend as much money on defense (?!) So car-oriented hellscapes are somehow the default, "normal" situation, because of course what you have accustomed to feels subjectively normal to you! Then Europe is some sort of a fairy-tale Disneyland that doesn’t need to face the Realities thanks to the US. Anyway, a nice claim but building and maintaining all that sprawling infrastructure is actually vastly more expensive than a denser, more sustainable urban fabric…
It can be both that in America we value sprawl and car-centered culture at great cost to ourselves, and that maybe it'd be nice if we pulled back on being world police a bit and invested more financially back at home. Maybe we could use all that money being spent on destroyers and forward bases to tear down all the stroads in the country and replace them with walkable mixed-use developments connected by rail.
In real life though, it's never that simple. Those destroyers and bases are being used for something even if it's stupid, and if they are no longer there, then things may change in unexpected ways.
The US doesn't get that benefit as the self-employed enforcer, and I'm sure we're all aware of how insanely massive the defense budget is.