It's... Not even comparable. That bomb is a quaint toy compared to modern nuclear arsenal, and of course nobody would be launching one or two nukes today because it isn't 1945. Mass starvation, disease, loss of key infrastructure and any sort of industrial capacity would await those "lucky" to survive initial blasts.

I'm not as convinced nuclear winter is a scare theory either, I think it's hard to say, but it frankly doesn't even have to factor in the slightest.

There's a difference between destroying one city with a relatively small bomb and destroying most cities and industrial infrastructure with relatively big bombs - including multiple hits on the biggest targets.