However, it's easy to change the mod so that it simply restores the previous games parameters as best as possibly, but does not proceed to start a new game with those identical parameters, leaving you to fiddle with your previous settings and make a few more changes... such as manually restoring the number of city states!
To to so, find the "function OnGameDebugReturn" this mod adds to Base\Assets\UI\FrontEnd\AdvancedSetup.lua on line 412, and near the end of that function remove or comment out the command "Network.HostGame(ServerType.SERVER_TYPE_NONE);" (line 454). You can comment out by prefixing with two dashes (--).