I recently changed my nations.txt as well, and it *does* show up in the game, so here are a couple of ideas off the top of my head.
Did you put the edited nations.txt in the database folder before you opened the game?
Did you start a new league at that point?
It's hard to know what went wrong without more information about the change you made, when you made it, and what you did after making the change. Anything else you can add would be helpful.
