I cant think of even the remotest explanation for the borders of the "midlands.".
Mapmaker A: Hmmm...what should we do with Ontario?
Mapmaker B: Make it its own region.
A: No, we can't do that. Our whole point is to show that Canada and the United States are actually the same thing and the border is totally arbitrary.
B: Let's make it part of something else then. Yankeedom?
A: No, Yankeedom has to be a narrow strip.
B: The Far West?
A: It's not very far west.
B: New France?
A: What part of "Destroy Canada" do you not understand?
B: First Nations?
A:
B: I have an idea! Let's make it part of The Midlands!
A: But then it wouldn't be contiguous.
B: I have an idea! Let's make a connection between the two in North Dakota! None of our readers have been to North Dakota, so they'll think it's cool and edgy and we've informed them about that unique cultural phenomenon that is Slightly-East-Of-Central North Dakota, which is more similar to Philadelphia and Toronto than anything else!
A: Great idea! Let's have it snake into northeastern New Mexico to make it even weirder!
B: Yeah!