There certainly have been conclaves of ethnic groups in this country. There were many in Wisconsin. My brother-in-law is Polish and comes from Milwaukee, which had (and has) a very high concentration of Poles and Germans. When early rock and roll was sweeping the country, the top ten selling records in Milwaukee usually included at least two or three by Louis Bishell and His Silk Umbrellas. A friend of mine taught school in Neenah-Menasha in Northern Wisconsin and most of the kids in his class had Polish names that were almost impossible to pronounce.

One of the best folk festivals I've been a part of was the North Country Folk Festival in the upper penninsula of Michigan. They involved all the local old European immigrant communities in presenting traditional music dance, dress and food from their native countries. I spent a weekend eating food I'd never heard of before (or since.)

Jerry