A senior couple living in the panhandle of Florida decide it's their time to go traveling, so they rev up the RV and head out. The U.S. has undergone a devastating nuclear war, and a lot of people are listless with radiation poisoning. In southern Alabama, they view the deep crater that obliterated the small city of Enterprise when the missile that was intended for Montgomery overshot. They gaze in awe at the 400 feet of exposed Coastal Plain strata in the crater walls. The floor of the crater has begun to fill up with water and a few abandoned cars.
The highlight of the trip is Atlanta, which had the indignity of being bombed twice. The first bomb would have sufficed. Now, interstate overpasses are twisted back over themselves by unimaginable forces.
It's clear that the couple will not last much longer themselves, as they too are succumbing to radiation. It's never stated outright, but one gets the feeling that none of the survivors of the nuclear exchange will still be there next year.
This short story was published, perhaps in the 1990s, in one of the news/literary magazines such as Harper's, The Atlantic, or The New Yorker. The title, if I remember it correctly, was Atomic Tourism or Nuclear Tourism, but no such title shows up readily on Google or the ISFDB. The author and magazine probably did not present it as science fiction, but it is a fine example all the same.