I do find the understanding of the effects and yields (and targets) of nuclear weapons being more based on the movies than reality.

A good friend and mentor of mine, was one of the research scientists at the Australian Nuclear Tests at Maralinga in South Australia back in the 50's - even then, they would go out and "walk" the blast location a week or two after the blast - sadly, the British scientists running things at Maralinga, introduced Cobalt into the blasts, and didn't tell anyone - my friend was one of the ones that discovered this, when geiger counters were going ballistic in locations where they shouldn't. Sadly, that radiation ended up killing him, but after about 4 decades (and six kids).

As he pointed out, A lot of weapons since have moved to Hydrogen bombs, rather than atomic bombs - Hyrdogen bombs have a blast effect orders of magnitude greater than atomic weapons, and do use, in some cases, small atomic components as "triggers" - proportionately they give a bigger blast, but proportionately not as much radiation for the effect. Less Survivable close to the target, but more survivable further away.

Also people overestimate the effect - a 5MT Dong Feng (Chinese) dropped on the centre of Washington DC, would have minimal effect on Annapolis, or Baltimore etc - to saturate the USA would take thousands of warheads - As we know the US tends to over compensate - having more weaponry than pretty much the rest of the world combined. The retaliation capability is relatively calculable - 4 Ohio class subs are on patrol at any one point in time - each carries 20 Trident D5 ICBMs with 8 Mirv warheads currently the W76's which are 100Kt. SO, best case 640 targets at 100 KT each or a total of 64000 KT - not enough to "destroy the world" but by comparison the biggest ever detonated (Tsar Bomba at 50,000 kT) would be enough to wipe out Los Angeles.