Traveller is, at least in part, a simulation of a genre of Sci Fi, not a piece of realistic Sci Fi in and of itself. It follows the convention, typical in Star Trek, older Doctor Who, Blake's Seven, ect, of unicultural worlds.
Now this is justified by the notion that each world grew either out of a single colony, like Virginia, New Zealand, or Pennslyvania, or out of the colonies of a single dominate power, like Australia, or the U.S.A.
The low numbers of states assumes that, as in Australia, Canada, Brazil, Argentina, Mexaco, and the U.S.A. The original colony simply claimed all the land as part of its state.
A reasonable Balkinized world for Traveller might have thre to five continents and continent sized island chains. Continent Alpha gets settled by Hindu nationalist/traditionalists determined to recreate their vision of India's past. Continent Beta gets several groups from Ireland who wish to raise their children as Gealic speakers, but otherwise they represent several different social visions. Gamma is settled by a group of genetically engineered humans seeking a place where they can escape social prejudice and live in dignity. Their social culture is American Midwestern with a few minor quirks. Delta is settled by excentrict liberterians, right-wing anarchists who despise government. The Omega Islands are settled by groups of refugees from a wide variety of Solimani cultures (mainly Asian and African) in a government run by a mega-corp whose goal was to maintain a starport and look charitable while aquiring coolie labour.
Beta and Gamma are functioning Representative Democracies, Delta is a complete mess, Alpha is a constitutional theocratic monarchy, and the Omega isles have become a crazy quilt of little dictatorships.
The Imperium would obviously prefer the Alphans. The Omegans and the Deltans would be disliked, but seen as manipulateable. The Betans would be seen as problimatic, and the Gammans would be seen as dirt.
