I'd say it's an amalgam of thoughts on pre-2000 social anxiety and heightened expectations and angst, and fears, channeled into hedonism by the counterculture, and consumerism by the mainstream (not that they weren't mingling) and society's addiction to the 24 hour information tap and how modern life is dependent on instant gratification, combined with their own jet-set lifestyle and of course as I remember this was one of-, if not the last song they worked on before sending the record to mastering, so there must have been a bit of running on fumes feeling (that permeates the whole of Pop, so it was maybe part of the: "what the f*** are we still doing here, who are we as a band, where do we go from the top of the world without a holy escalator", plus the beginning of a midlife crisis) , so it all added up nicely into an apocalyptic fantasy strolling down Main street.
Way to predict the internet age by the way.
Also there happens to be a Ray Bradbury short story that takes place on the last evening/night of humanity, with everyone just knowing there won't be a tomorrow. No meteor, no known cause for the end of the world, just the certainty nobody's going to wake up the next morning, even nobody being there to wake up. Wonder if Bono's read that, or a similar literary work.