> Europe, where public transport is really practical, and cities are built for density
Hmm, European cities weren't built for commuting or public transport, almost all of them were laid out in the medieval era for walking. They then acquired one or more railway stations in the 19th century, creating commuter ring #1 and becoming an order of magnitude larger, and may have been partially redesigned for cars in the 20th century, creating commuter ring #2. A popular conversion was demolishing the medieval-era city walls and replacing them with a ring road. Some were entirely flattened during the war, although generally rebuilt on the same plan.
Now most American cities were by comparison entirely designed for commuting ... by car. The problem with car commuting is that once you're over capacity it slows down the experience for everyone. Public transport just jams you in physically, which was uncomfortable before the pandemic and now just a nightmare. An overcrowded train is not slower than an empty one. (Subway throughput can be embark/disembark limited, though)
The difference to me seems to be the walkable core. That in turn depends on norms about use of public space and perceptions of public safety.
I'm slightly biased, but I think the Edinburgh New Town design with a couple of modern adaptations could be the ideal even for the 21st century. Grid layout, four to six floors, high ceilings, decent size windows, wide streets, occasional shop on the corner or restaurant in the basement.
("New" here means 18th century https://en.wikipedia.org/wiki/New_Town,_Edinburgh, not "new" as in postwar new town or medieval New Forest)