Earlier quoted context omitted.
==everyone is the same ethnicity and culture== I think depends on how you define ethnicity and culture. Sweden foreign-born population - 17.0% [1] US foreign-born population - 13.7% [2] [1] https://nordic.businessinsider.com/swedens-foreign-born-popu... [2] https://www.reuters.com/article/us-usa-immigration-data/u-s-...
Using just the census designated measures would be a fine start. Foreign born population wouldn't begin to address diversity in the US. In Sweden it might be the case that foreign born population is the only source of ethnic diversity. Whereas in the US, the people in northern Maine live in a completely different world than the people in Southern Florida.
And your contention is that Stockholm, Malmo, Kiruna, Haparanda and Skalstugan are all the same?