For example, the state of Illinois is a city-state because, despite its large physical area, two-thirds of its population lies within the counties that make up the Chicago metropolitan area... These are the fourteen states (plus the District of Columbia) where over the half the population of that individual state lies within a single metropolitan area...More discussion at the link, along with the numerical data for each state (MN = 59%, WI = 27.6%). Further commentary at Yglesias, who notes -
More generally, these city-states don’t fit a single category in my mind: they are on both coasts as well as being landlocked, and encompass the non-contiguous states of Alaska and Hawaii.
I think this is mostly a glance at how poorly designed our currently political boundaries are. The definition of a metropolitan area is bound to be somewhat arbitrary around the margin, but these are real social and economic phenomena. But we make important political decisions at the state level. That’s not just state government, it’s senators and the electoral college as well. Some states—California, Texas, Florida—are way too big and encompass multiple major metro areas... There’s a huge continuous swath of land in Nebraska, South Dakota, North Dakota, Montana, and Wyoming that gets ten senators and has fewer residents than the Detroit MSA which doesn’t even get to dominate a single state.
Something worth noting is that while overrepresentation of low population states was obviously part of the original constitutional bargain for a reason, this is a different phenomenon. Late 18th century America was such an overwhelmingly rural country that the whole question would have been irrelevant. Meanwhile, some of the metro-dominated states are also low-population states.