My setting takes place in a post-apocalyptic america, and is in many ways a classic 'great war ends world' sort of thing. However, the cataclysmic ending to most of the country is persistent, lethal radiation that lasts way longer than it normally could from an atomic bomb. As such, most places are intact, and are made from high-grade materials whose frames don't decompose even after the timespan of 200 years, which is how long it has been since the war in this setting.
Because most of these people died from being irradiated, and in most places there are little to no organisms (except some radiotrophic fungus and bacteria), how long do you think they would last? I know climate is a major factor, but I'm essentially designing the setting across the country, so the climate can vary tremendously, and I'd like to know the answer for basically all of them.
I think this is a tough question because of how alien the concept is, but I'm hoping you might have some more insight than me.