If it makes you feel better, while its has been possible to completely level everything within the M25 with a single nuke since the 1950's its almost unthinkable that any country would ever commit to the use of such weapons in this day and age, not for any moral reason (of which the are many) but because its strategically pointless.
The bombs dropped on Japan were designed as a shock and awe tactic and were used not to kill but to save lives as Japan had never surrendered and would have fought to the last man if the allies had been forced to invade the mainland, this would have caused many many more deaths on both sides than the nuclear weapons did.
Old style large atomic bombs carried by planes have been replaced nowadays by smaller nuclear warheads carried by missiles which are not as effective but more precise. And in the day of satellite surveillance you don't need massive explosions to ensure you get your target you just need precision hits.
Added to that nukes are pretty obsolete now as we can build fuel air bombs (conventional weapons) even more destructive than the WW2 nukes and the whole idea of nukes is pointless for anything other than striking fear into your enemy.
