I mean, NYC has a ton of culture but it's a young city.
I disagree with you premise.
And if it's not what I managed to communicate effectively, I can assure you it is not at all my intended meaning.
Which would then falisify your own premise.
But Iād argue NYC has more culture than say Edinburgh, Scotland despite the later having a far more extensive history.
Contrast though US cities of roughly comparable population (506,000 for Edinburgh), say, Sacramento, CA; Kansas City, MO; Mesa, AZ; or Atlanta, GA. Two of those are also state capitals, roughly matching Edinburgh's political status.
Remmeber that size was another key factor. Again, not sole, but key.
Global cities ratings gives additional ratings and bases for same:
https://en.wikipedia.org/wiki/Global_city
GWAC ranks Edinburgh above all of the US cities, save Atlanta, which is just above it. Mesa and Sacramento are not ranked.
https://en.wikipedia.org/wiki/Globalization_and_World_Cities...
Few American cities were founded > 200 years ago. None were founded more than 1565 (United States), and the oldest dates from 1502, Santo Domingo, Dominican Republic.
That said, what a New Yorker visiting small-town Europe is probably referencing is the contrast between NYC and Small European Town. The specific town will likely be largely interchangeable with numerous others of similar description.
By contrast, a small town in the US or Canada largely resembles some of the less-distinguished suburbs of NYC itself: same language, same government, same mass media, same history, same chain stores and franchises. Far fewer people, however, and a much smaller economic and cultural ambit.
Even for small towns in which there is some distinctive culture ... it tends to be a single motif which dominates the entire town, rather than the melting pot of a major metropolis. Marfa, TX; Silver City, NM; Santa Fe, NM; Asheland, OR; and Napa, CA all have distinctive cultures, but it tends to be all-of-a-type.
Exceptions tend to be smaller college towns, for obvious reasons, but even here, the odds for highly-diverse communities tend to be lower than in larger cosmopolitan cities. And you can climb far up the major metro region and still find fairly stultified culture --- Chicago, IL, wears its "second city" moniker as a badge, but you'll still find there's some real edginess there about it if you press a bit or scratch beneath the surface. (The fact that it's third by size, and that Los Angeles also evinces a somewhat similar attitude toward New York doesn't help.)