I wonder if you could have lots of small meteorites instead of the single big killer one? There's clearly a size between having bugger all impact other than a tiny crater, and wiping out a continent, so sort of in there somewhere?
That would basically be the same POD as The Peshawar Lancers, but a few decades later. Which might be quite interesting, though as someone noted the effect of a catastrophe that major wouldn't be that different whether or not there was a war on (except for perhaps more people attributing it to divine judgement).