Yep very few of us can fathom the power of a 5, 10 or 20 megaton device. Pretty sure I can die happy without one ever being set off over anyone's homeAt that time, probably. Even as kids we all suspected that an atomic bomb was bad, but in hindsight, we didn't have near the information at hand as we do today.
Given what most people know today...the profound damage caused by "relatively small atomic weapon", a couple of miles or so away from the point of detonation would probably, at the very least, do some serious cremation to everything in the blast range. And I guess that close enough to detonation that the blast would actually evaporate people, places and things.
Again, despite the fear that existed in those days about atomic bombs, I seriously don't recall that kind of devastation hitting home in the minds of most people...especially kids.
I think the reality hit home with me when I was a kid and saw a movie with Mickey Rooney called "The Atomic Kid".
I happen to watch a bit of the destruction of a half-mile wide tornado that came within 2 blocks of our home (in Dallas). I can't remember how many miles that it ran its course. My grandmother finally grabbed me off the front porch, wrapped me in a blanket, put me in our clawfoot bathtub. Our windows were shattered, debris made its way inside our house. And significant size debris was scattered in our yard, along with everybody else's yards along the path. It took us weeks to clean up after that incident and we weren't directly hit. Buildings that were dead in the path of that tornado, and which were similar to school structures at that time, were leveled. I still get a quiver from time to time thinking about that day.
EVERYBODY TODAY knows what the consequences can potentially be. But really, I don't think we really know what atomic weapons are capable of in present time. They can probably make an atomic weapon the size of an iPad that can do the damage done to Japan during WWII. Who knows? All governments lie so much.