Yep. Make sure the country list matches in the NEK.xml or whatever single mission campaign you specify in the game.xml. Also match countries in the country.xml and pilotconstants.xml
While I had no issues with the cutscenes.xml trim (Notepad++ makes the job easier!), my attempts with country.xml were not so good so far, and had to put back my original. Maybe I made an error somewhere. I don't see a need to mess with the pilotconstants.xml