I think most of the inequality between teams had to do with the team distribution, some of which is inevitable. My favorite option to help address this is:

Have 5 teams of 7, but have team captains pick the countries. But the process would start with each captain getting to pick a N. American country, then a S. American country, and so on through Europe, Africa, and Asia and the Pacific (grouped together), before repeating until all the countries have been chosen. This way, the success or failure of the team distribution would rest with the teams themselves. Captains could be comprised of players with certain minimums in number of games played here, points, and reliability rating.

Regarding 7 teams of 5 , after reflecting on the spread, I agree with Germany, who notes: "How do teams coordinate when they're all spread out like that?"

Regarding localized groupings of teams, I agree with Mexico, who points out: "The problem with Historical or Localized teams is the same one we see with Russia/Central Asia. Inevitably these groups will become self-sufficient in defense really quickly, and will be unable to be really destroyed during the game."