Every country would see significant death totals from a very
large scale nuclear exchange. 50-100 nukes would as you say be far less significant, but do 100x that and you get more worldwide impact.
The thing is, there isn't going to be any large scale nuclear exchange. For one, North Koreans don't have that many bombs. On the other side, it wouldn't take that many bombs to glass the entire country of North Korea.
During the Cold War, by contrast, the Soviet Union had approximately ~48,000 warheads.
During the Cold War, by contrast, the Soviet Union had approximately ~48,000 warheads.