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.