There's nothing about culture that ties it permanently to race, if that's what you're insinuating. Racial diversity does not imply cultural diversity - which is an incorrect shortcut that I've seen most people who deploy the "but the nordics are not as diverse" argument - especially American whose media consumption tends to be more insular.

I think there's a fallacy at play - not sure which one it is, whereby a person sees a lot of nuance, variation and detail in the minutiae of what they are familiar with, but the unfamiliar is painted in very broad strokes, lacking nuance, and based on surface-level understanding.