Having grown up around Chicago, it is most definitely a city-state unto itself, with the collar counties of Cook, DuPage and Lake in the orbit as "the Chicagoland Area". Lumping it in with south-eastern Wisconsin doesn't seem right at all. (Perhaps Chicago could annex Lake Geneva, WI in much the same way as they annexed the land out to O'Hare. *heh* Lot's of Illinois plates in LG in the summertime.)
Wisconsin (where my family comes from on both sides) has a sort of east/west demarcation as you've described. I'm still trying to sort out how Milwaukee (Mom's side) fits in with Taylor County (Dad's side). Both are fairly different from south-western Wisconsin (wife's family).
Edit: I'm chuckling at how small Missouri got. My folks always joked that, in fact, Iowa was not a real place at all and was just a blend of South Minnesota and North Missouri. Especially Keokuk, where our friends were from.