Hey we Kansans have hills lol
There's the Flint Hills for example lol (photos was when the grass is dormant):
Granted where the fictional town of Jericho (closer to the Colorado border) is roughly located at in real life cities in Kansas is far from the Flint Hills. Plant life for sure though is a dead give away that it's not in the area it's supposed to be.
But the majority of Kansas is more flat though.
But honestly many movies aren't made in their respective locations-I know Atlanta for example is used a lot because their industry has tax breaks, etc that lure people in, Canada also has a more friendly filming location. I do laugh though when a tv show or movie has a setting in my area and it's clearly not my area lol.