Where are you from, and where have you lived, visited, and worked to come to this conclusion?

It's not at all what I've experienced as a US born after living on both coasts, a few different states, and a range of small rural and large urban cities.

Food sure, if you only consider culture as the corporate branded chains. That's missing out on a lot though.

Language, accents, nomenclatures, sayings, mannerisms, all widely varied.

Religions, there are dozens of Christian based sects all with widely varying spectrums of beliefs.

Work culture, still many good-ole boys clubs in certain geographies, pick yourself up by the bootstraps types in others, and anything you can imagine in between.

The OP specifically said compared to regions of similar size. You only talk about variations in the US, have you lived outside? The variations that you talk about, you can find in Germany alone which is the size of a medium size US state.

The variations across Europe (I can't speak for India) are on a completely different level. If you put a random person into two different states in the US and two different countries in Europe for an hour and ask them after which differ more, I would bet serious money they will always pick the two European countries.

> Europe for an hour and ask them after which differ more, I would bet serious money they will always pick the two European countries.

Only because of superficial things like language. When it comes to politics and the role of government, Europe is pretty consistent. Barring language and architecture, this makes cities all effectively the same pattern (high density, trains, buses, expensive per sq foot).

The gulf between life in the sprawl of Dallas and the density of NYC is far greater than the difference between Paris and Rome.

OP also conflated regions and countries. I read it as they were comparing US, EU, and India as a whole. Also curious where their perspective came from.

My point is that the presence or absence of cultural variation in one place does not equate to a lack thereof in another. Just because someone hasn't seen it, doesn't mean it doesn't exist. Culture isn't based on comparison, it's something in its own right

While the US has basically every current religion there are huge regional differences in which religions are common. Mormons for example are still extremely concentrated in Utah. New Jersey has a much larger Jewish community than most of the US etc.