Americans don't really consider that the Korean War was the first real conflict of the Cold War, and as such was conducted when things weren't exactly cold. Neither the US nor the Soviet Union could nuke the other out of existence but both could nuke each other. Targeted bombing didn't exist and strategic bombing had won WWII. As a result, we treated North Korea as if it were Dresden or Tokyo and smothered it in ordnance.
For Americans, the journalist Blaine Harden has written, this bombing was "perhaps the most forgotten part of a forgotten war," even though it was almost certainly "a major war crime." Yet it shows that North Korea's hatred of America "is not all manufactured," he wrote. "It is rooted in a fact-based narrative, one that North Korea obsessively remembers and the United States blithely forgets."
Important side note: As Robert Kaplan points out in Asia's Cauldron, Americans have an overly-important sense of our own impact on the Asia Pacific region. Most Americans, for example, think that Vietnam as a country is deeply resentful of the US for the Vietnam War, without recognizing that while the US occupied Vietnam once, the Chinese invade regularly and continue to be Vietnam's biggest trading partner. America is very much North Korea's biggest bugaboo but that's only because the Japanese are gone.