I get your point, but I'd have to disagree with it. (I should make a note that I'm Canadian and I've travelled extensively in the US and semi-extensively in Canada)

I think that Quebec & Alberta/another English-speaking province probably have more cultural differences than any two US states, not including Hawaii. Hawaiian culture is so different, by virtue of its distance (it's not even in the same continent as the rest of the States) and its relatively recent statehood. I would make the same argument for the US territories (Northern Mariana Islands, Guam, Puerto Rico, and perhaps the US Virgin Islands to a lesser extent). Can't really speak for Alaska, as I haven't been there, but I would imagine that the sizeable Inuit population has many cultural differences from the stereotypical "American."

Another thing to point out is that the US does have more diversity than the average country. Saying this will inevitably get me downvotes, as this sub can be so anti-American to the point of blind vitriol, but it's true. Even before colonization, there were thousands of indigenous tribes very diverse from one another. Though much of that culture has been lost, when we talk about how the US isn't that diverse because it's all English- (and maybe Spanish-) speaking, it's all Christian, it's all primarily conservative when compared to other Western countries, etc... we forget the diversity shown in the original inhabitants of the land.

I am, of course, not defending the idea that each state is like a different country, as that is a ridiculous American-centric and ignorant viewpoint. But it's just as ignorant and ridiculous to claim that the US isn't a particularly diverse country. (Note: I'm not accusing you of thinking this; I've just seen this sentiment on this sub before)