"Nuclear war is overblown, we barely have enough weapons to blow up the top 100 major cities"
How do you figure that? No, a nuclear war won't "destroy the earth" as in sterilize it, but a few billion dead followed by mass starvation among those left would be pretty apocalyptic, not "overblown".
Number of warheads by country:
USA: 3,750
Russia: 5,977
China: 350
UK: 260
France: 290
India: 160
Pakistan: 165
Israel: not known but estimated at around 90
I agree that it's difficult to imagine a scenario where all the nuclear powers are launching everything they have at each other all at once, but if it did happen, it would mess up a lot more than 100 cities.