That was a good book. Very underrated. I also liked his alternate American history where the Americas were populated by Neandertals rather than American Indians; I think the stories were collected in a book called A Different Flesh.I like Turtledove as well, but I haven't read his Civil War stuff except for The Guns Of The South. I've read all of the Worldwar books, though, as well as The Two Georges, which he co-wrote with Richard Dreyfus. (I asked him once, "How much did Dreyfus really write?" The answer I got was "Quite a bit, actually.")
I don't really see the Cold War erupting into conflict around 1990; the internal situation in the Soviet Union had been degrading for too long at that point. What interests me more is a nuclear exchange at the time of the Cuban Missile Crisis. There definitely could have been an exchange of nukes between the US and Russia at that point that would have caused some serious devastation. The US would have gotten through it, but the Soviet Union would have likely collapsed in internal conflict as the member states took advantage of the situation to secede. Today's world would be completely unrecognizable.
In World in Conflict, it was presented rather plausibly. In 1989, the Politburo decides to threaten Western Europe with invasion in order to force them to send aid, but this plan fails and the Soviets end up forcing an actual invasion. After a time, NATO regroups and receives reinforcements from the USA, fighting the Soviets to a stalemate in France. It's not long after this that the Soviets launch their sneak attack on the American west coast.
Don't forget the Chinese assistance of the Soviets! =)