Where It All Goes Down
Australia
One of the unfortunate side effects of a nuclear apocalypse is that it doesn't leave many locales left to visit. Because of this, we spend the bulk of On the Beach in sunny Australia, with our few glimpses of the outside world raising more questions than answers.
Livin' in a Land Down Under
Fortunately, we get to know ol' Aussieland quite well. Sometimes we chill in the country, which Dwight gleefully compares to "'a small town in the States'" (4.216). Sometimes we party in the city of Melbourne, where the citizens are getting wasted on a 24/7 basis. And sometimes we head to work at the naval base in Williamstown, which—amazingly—still runs like clockwork. Seriously, you'd be hard pressed to find any evidence of the coming apocalypse—aside from the total absence of cars—at the beginning of the novel.
As the end draws closer, however, we see a marked shift in the country. It happens first in small ways: cars suddenly appear on the roads, as people have no reason not to bust into their secret supplies of gasoline. Then the partying stops—which, frankly, is a relief. Finally, the city of Melbourne is reduced to a shadow of its former self: "The streets were dirty now and littered with paper and spoilt vegetables" because it has been "days since the street cleaners had operated" (8.129). This, sadly, is our final glimpse of the city we've fallen in love with over the course of the novel.
Fallout
The rest of the world has met a similar fate, of course. Although Dwight and company cruise all over the world in Scorpion, radiation prevents them from actually checking out the land. Still, their tiny glimpses of their "home country" of America are striking—even something as "uninteresting" as "a cafe with a Buick parked outside it was enough to set them talking and revive starved minds" (6.19).
Interestingly, it's the lack of physical damage in the affected areas that's so striking to us. There aren't giant craters. There isn't any steaming wreckage. If you didn't know any better, you'd probably just think the entire town was on vacation. That's scary. If you ever wondered what that whole "not with a bang but a whimper" thing was about, then consider your question answered.