Us politicians and other groups use the fall of the empire to support their ideas. greek rome han

I believe it is both Greek and Rome, but more of Greek
 Greek is mentioned in relation to democracy, especially the weaknesses of direct democracy, where citizens would congregate at the mount to air their views and elect the candidate of their choice. The candidate who had hired the most talented shouters often won. The limitation of mob type of democracy informed the rationale behind the electoral college.

Rome is mentioned in relation to the course of imperialism on national cohesion and stability, as well as the capture of a good democratic course by totalitarian regimes.

In the midwest because it has more moderate climate than the north or south west which makes farming far easier.