[wyum]

I also grew up in the US. In my high school we read the book "Hiroshima" by John Hersey, which tells what happened that day, according to survivors. I recall it being a powerful read. Gave me a tremendous amount of perspective and empathy for the victims.

There is some historical evidence that the US dropped leaflets warning about the impending bombings and the atomic bombs specifically. For info, Google "LeMay leaflets." It's also likely that the US made AM radio broadcasts about it. Even so, I'm sure the Japanese citizenry would have regarded it as the enemy propaganda it was and largely ignored the messages. And of course no one could have anticipated or imagined the atomic bombs.