Not true. Vast yes, but diverse, not so much, unless you're specifically referring to wildlife and not to people. Coast to coast you'll find the same language, the same religion, the same sports, chains, food, traditions, holidays, it's all the same. To you, the differences between a Texan and a New Yorker may be huge, but to outsiders they're the same thing.

Travel the same distance in any direction in the old world and you'll find dozens or even hundreds of languages, completely unrelated cultures, cuisines, traditions.