Here the Korean War is a non-issue. It's probably as forgotten as the Spanish-American War. There it's not. Some cultures view honor differently. Those cultures, if there's a national defeat, dwell on it until it's a large cancerous growth on their national psyche.
If your culture isn't into public honor, or chucks the concept to a large extent, then losses aren't such a big deal. They make make you angry, but not in the same way. Centuries of repression left Jews, for instance, able to joke about their status and find ways to have dignity in spite of it.
In other cases, it festers until it bursts forth in unbridled jingoism as soon as the physical and technological base is sufficient. This was Germany in the '30s. It's increasingly China and Iran. Usually when we read contemporaneous reports of those countries in the English-language press all of that gets deleted as propaganda and hyperbole, as filler of no interest to us. It's a kind of cultural blindness. It was nonsense in the Russian-language press in the '80s and '90s, until Putin rode it to power: The "filler" turned out to be the news, but even then most reporters, northerners or native to mostly Puritan and Enlightenment ways of thinking, thought it just short lived. This kind of thing finds no resonance with us, it's hard to understand, to sort out, and requires sustained attention of at least 30 minutes. Making it easy to understand how most Americans can't figure it out.
It's the same kind of trait that makes Fourth of July a kind of vacuous holiday in the US. We don't dwell on national defeats. We ignore them. We don't dwell on national victories. Heck, we pretty much ignore them, too. Well, many of us do. Some don't. There are subcultures in the US that still bear a strong imprint of public honor. They have higher rates of murder, more fights, and some tend to carry flags to remind them of their defeat.
If he was going through passport control and the agent said, "How did you enjoy your stay?" or "Did you like our country?" and he responded, "Better than the last time I was here, during the war" it would have been enough for some pre-offended jingoist to report him. The timing's right, too. And on the way out he'd have been more likely to let down his guard.
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