Can a country have both unity like the Romans and diversity if yes how if no why not?​

Yes i do believe they can. Indonesia, for example, their motto is Bhinekka Tunggal Ika (Unity in Diversity). Despite all the differences in its multi cultural society, there is a sense of unity among all people there. this is maintained by respecting others choices and their backgrounds and allowing interactions without questioning someone’s religious, social or economic standing.

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