Realistic perhaps, but you also have to try to balance gameplay. Feel free to download those unfinished scenarios and change them any way you see fit.. I haven't touched them in this form in years, nor will I return to them, though they are a major influencing factor in the Destiny reborn mod...
In DR, all 200+ countries of the world have condensed into 31 countries as WW4 breaks out. The smallest countries band together for protection. The larger may stay untouched or absorb their smaller neighbors (all this based on population). Independent territories leave their parent country, become independent nations, then get reabsorbed into the closest nation to them. For instance in China, Hong Kong, Macau, and Taiwan form their own nations, but Hong Kong and Macau later get reabsorbed into China, while Taiwan joins the Phillippines. In the US, the Virgin Islands, American Samoa, Puerto Rico, and Guam all form separate nations, with VI and PR joining El Caribe (Carribbean nation) and American Samoa and Guam joining Pacifica (Pacific Nation).
A sub-scenario I considered but will likely never get to is the North American version, in which the US States, Canadian Provinces, and St. Pierre and Miguelon call condense similarly into the new 31 states that make up the Unified States of North America, and have themselves a fun little Civil war. I have the states mapped out but that is as far as I got there.