The Old World
So in this alt world, most things are the same, WW1, WW2, and the Cold war still happen with no change, its after the cold war that changes,
After the USSR collapsed the world continued to march forward industrially not really caring about global warming or any enviormental issues mass industrialization caused.
Sometime between 2000 and 2040 global warming overtook the world, as the mass industrialization never slowed down leading to the earths tempeture increasing and flooding the globe, as flood waters rose and nations begain to panic and fall Governments across the globe paniced, and in desperation lashed out and attacked countrys as they flooded and collapsed, quickening a global collapse of all nations.
Out of the Ashes
Out of the ashes of the old world new nations are born, some cling to the ideals of the old world while others toss them aside and march forward. Starting time would be around 2060 or 2070 to allow the nations to be as estableshed as they are.
(this above would be the basic setting of the Pax Americana RP, so the flooded map and different nations would work well! If you have any tips, questions, or ideas lemme know)