Earlier quoted context omitted.
Nuclear winter seems unlikely to me, and from what I understand I'm not alone. Cities are no longer prone to huge firestorms like they once were. Furthermore most nuclear strikes would probably be airbursts to maximize blast effects, but that means less material being thrown into the atmosphere. If the attack were calculated to cause maximum fallout instead, airbursts of salted bombs might be used, which would poison…
The primary targets for nukes aren't cities, they're other nukes. Most of these warheads are set for groundburst (or underground burst - I remember a bunch of research in the 80s about burrowing/penetrating warheads), because to blow up a 3-4 foot thick reinforced concrete silo you basically need to land right on top of it. That's the big fallout threat.
Some napkin math: the Sedan test was optimized to dig a big hole, was buried almost 200 meters deep, and moved about 11 million tons of earth, leaving a crater of 0.005 cubic kilometers. The 1815 eruption of Mount Tambura, which caused a 'year without summer', ejected 160-213 cubic kilometers of material into the stratosphere, something like 32 thousand times as much as the Sedan blast. I'm guessing each strike against a nuclear silo would probably create craters a fraction the size of Sedan.