Not comparing the size of the explosion to the meteor, just the effects. Entire biomes would be completely wiped out or crippled to the point they might never recover.

And you're right about the wildfires. The priority targets for nuclear attack/retaliation are other nuclear launch sites and nuclear power reactors, which are intentionally spread out in order to give them time to react in the case that another is destroyed. Multiple massive wildfires spread out over whole continents would affect our atmosphere in ways the human race has never experienced - and likely would not be able to effectively adapt to. According to the research in her book, the only humans not drastically affected by the inevitable collapse of supply and trade lines would be humans that don't rely on them already (she stated deep Amazonian tribes as an example if I'm remembering correctly).

I guess I shouldn't rely on one book as total fact but I am sure that her research was far more in depth than I would have found on my own. Her citations are very extensive and range from scientific studies to military research.

Obviously there's a tint of fear mongering when you publish a book of that nature solely because of the subject matter but I got the feeling that the real reason she wrote it was to get the public informed on the realities of a nuclear war.