I remembered something that Hoshi said in one Enterprise's episodes, I think in season two or three. It was that the other nations of the world were scared and very jealous that the Vulcan ship that landed on Earth in 2063 happend to land in the United States of America. I'm surprised that the American government didn't use this to their advantage and try to isolate the Vulcan technology from the other countries. The Earth was united yet, and old rivalries still existsed, I'm sure. The formation of the world government is still about 50 years away.
In my opinion, this leads to a lot of speculation. World War Three details are so vague almost anything could have happend. We know there was ECON, or the Eastern Coalition of Nations, and they fought the west, or at least the United States for sure. I would assume that ECON was dominated by China, or maybe even India, or something a little far-fetched, an Indian-Chinese alliance/single government.
It's obvious that the USA survived, and from a military stand point, won the war. According to canon Star Trek, the USA survives to at least 2079. What I want to know is, what was the damage to the globe. What was destroyed, which countries collapsed, how did the world change, who survived?, etc.
To me, it felt like World War Three wasn't so terrible, only becuase they never say what the hell happend. I know 600 million is a lot of dead, and is terrible, but it didn't feel like such a huge crisis, unlike a few other nuclear events in some other moves and TV shows.
Just my two cents. Random, I know.