Sterling did it in the Peshawar Lancers, using a comet and subsequent tsunamis to destroy most of the western world. This isn't really the focus of the book, but it is mentioned that people in the wreck of Europe are now reduced to making crude tools from scavanged railway tracks, the only viable source of steel.
All things aside I'm gonna echo what has been said, the idea of a gilded age "Fallout" is conceptually stillborn. The premise of post-apocalyptic scenarios arise from the tension of a looming catastrophe, nuclear weapons or climate change etc. No such real overhanging catastrophe is present in the gilded age neither in spirit or in the political field.
To most victorians the closest you came to a post-apocalyptic scenario would probably be some kind yellow-peril scenario of the "mongoloids" conquering the civlized world, most likely sparked by the Russian Defeat in the Russo-japanese war, which is a bit late for a truly steampunk/victorian fallout scenario (which I assume is what you are going for). Also it's inheriently racist and horrible.