I think the casual dismissal of nuclear war has more to do with the artificial nature of most people's realities than a lack of a direct demonstration of the destruction of nuclear war specifically. People think it can't happen because the majority of people's lives in the developed world are heavily distorted fake marketed/filtered/scripted stuff optimized to do what they want. People love spectacle, they're used to being insulated from the effects, and they think past concerns are like boring stuff from an old season of a TV show.

I think wilderness camping is the best counter to that kind of thing. Sounds unrelated, but it's one of the most visceral, instinctual ways to get people to remember the reality of physical consequences. Those consequences exist no matter how frustrating or stressful they may be to deal with. If you leave food out, it spoils/you have no food. If you can't find water, you have no water. If you don't sterilize the water/check the source, you get sick. There's no grocery store, no cops, no social media to get support from, no emergency deliveries, no doctor, no credit to extend... nothing but nature and what you carry on your back. If you screw up, you're screwed.

I only did a couple trips like that, but when I got back to highways, cars, skyscrapers, restaurants, etc, I appreciated how amazing it all is, and how it's basically all just a very, very big, complicated campsite that's been built up over a long time. Nothing manmade is a given, and the only thing keeping it together is us. Nature is way bigger than you, and there are no guardrails. If someone launches a nuke, it's not a strategy game or a movie. That's a cliff you don't want to walk anywhere near.

A one or two week backpacking trip in the middle of nowhere should be a graduation requirement, imo. Would have lots of benefits beyond just added perspective about the reality of physical consequences.