pespective- The impact that caused the Chicxulub crater, likely a leading cause of the dinos extinction, is estimated at 100million megatons. thats got to hundreds of times the destructive power of all the nukes in the world combined- so at best, maybe we could do just as good a job. But I doubt it. a big reason for the extinctions is the sunlight being blocked for like a year, and that would have caused the extinctions in the ocean. the plankton dies, in turn everything else does.
The oceans, I doubt would care about a nuke war.
This is a great angle.
Actually however, the Chicxulub impact was far more deadly than the nukes would be - not only because of the huge size of the comet/asteroid but mostly because the impact angle was oblique at about 30 degrees (so the impacter hit on a sharp angle and not straight down). This meant that the bulk of the energy from the impact went into the atmosphere and not into the ground as most impaters do. As a result of that, many millions of tons of rock and molten ejecta were blasted north and literally scorched all of the present US and Canada just about. It was for this reason, the unique nature of the blast, that cause the extinction of the dinosaurs (and there is now plenty of verified evident, its no longer a question).
The effects of nuclear war - even en-mass - would be different but equally devistating to the world. Chiczulub produced no radiation, but the huge atmospheric blast caused a world-wide fire (all forests, literally). Nuclear bombs wouldn't do that, they would annhilate totally the areas around the impact - but it wouldn't cause a world-wide firestorm unless bombs landed in every single forest - BUT the fallout would most definitely be world-wide, the sky would definitely darken - but not for as long as Chiczulub did (primarily because sulfer dioxide can stay aloft for years, but fallout wont). The nuclear winter would be quite short compared to the Chiczulub winter as a result. This difference is quite huge, as with Chiczulub the winter lasted long-enough to kill off about 70% of life in the Ocean (only the deep-sea creatures survived). A nuclear war would not do that, and the ocean would still have Alot more life in it than post-Chiczulub.
I think the biggest difference between them is that with Chiczulub - no place on earth was safe from being roasted alive. With Fallout, no place on earth would be safe from being irradiated to death. To me that means lots of ghouls and mutated life, but still lots of life around. With Chiczulub, the majority of life on earth perished. To me it makes alot of the "theme" around Fallout seem plausable. If a game were made in the post-Chiczulub time, there wouldn't be much to do or see.
Again great angle, love the anology!
Miax