In the midwest, there are plenty of trees. They just happen to be at the edge of fields as windbreakers and in waterways, as conservation efforts. Kansas is a lot more arid than Illinois and Iowa, so it has fewer trees, but as far as I know, it's still pretty treed. It's mountains I object to, and I don't remember seeing any in the show.
Like I said, it's worth watching. There are quirks that show it's not a typical midwestern town, but in this day and age, are we really going to put a show on TV that isn't diverse?
I think though, that the guy from "St. Louis," as he claims to be, is in a perfectly plausible situation. He's the only black guy in town--I didn't see too many people of other backgrounds. In my town, we were about 90% white, but we had a number of Latinos who descended from migrant workers, so it's not completely impossible for a small midwestern town to be diverse. The next town over from ours *did* have quite a bit of diversity, as well, so it's not like the midwest is an island of whiteness--it varies from town to town.
However, like I said, that's minor compared to the potential this story has, and I want to see where it goes. I still think it's the best show of all the new ones this season.