The reason I don't see Chicago as very Midwestern might be a "very BRTD" reason but it's because "ethnic whites" actually are a thing there, as is "cultural Catholicism". Pretty stark contrast to like Des Moines or Madison or of course right here Twin Cities.
Bit cherrypicked, doncha think? Des Moines and I think the Twin Cities were underrepresented in the most recent waves of European immigration in the early 20th century, and the same applies to Madison which is very much a "new economy" city. Meanwhile I think just about everyone would call St. Louis, Milwaukee, or Cleveland Midwestern.