I've edited the cities.txt and nations.txt so that if you use these you can create a league that only has players from Michigan and during initial creation will only have Michigan cities. It was pretty easy to do, but I just thought I share it for anyone interested.
Just in case you don't know, the way to make this work is:
1. Rename the original cities.txt and nations.txt. I just rename the ORIGINAL_cities.txt, or something like that, just so don't foget.
2. Rename the Michigan_txt files to just cities.txt and nations.txt. This will make them the defaults.
3. With these in place, the next time you create a new league all of the cities and players will be from Michigan.
4. Remember to switch back to the original txt files if you want to play other worlds or else you'll still have just Michigan players 
5. Enjoy.