A deliberately provocative question; but ignoring the human and moral element (to the same degree as the thread debating the Third Reich’s efficiency in killing concentration camp inmates), if somehow China and India suffered cataclysmic destruction and loss of life, would the USA derive a net benefit from it?
Consider the quarter-century after the end of World War Two, roughly the twenty-five years from 1945 to 1970. An era considered America’s Golden Age as Europe and the Pacific Rim spent decades recovering from the devastation of the war. Which not only didn’t touch the US but left it better developed than ever, and in a prime position as the chiefmost manufacturing power in the non-communist world.
So let’s say that a comet or asteroid impacted the eastern hemisphere. Rather than a single huge strike, once the comet passed within the Earth’s Roche limit it broke up into a multitude of smaller bodies, peppering an arc of destruction from China to India. The equivalent of thousands of nuclear blasts ranging from kiloton to multi-megaton in severity. The devastation is immense, and from both direct deaths and the chaotic aftermath over a billion people in the two countries are dead in a few months.
So how is the USA affected, other than possibly a year without a summer? In the short term losing cheap imports and outsourced services would hurt; but by the same token jobs would be created. Maybe much of the debt we owed would simply cease to exist, obliterated by the extinction of the governments holding it. What was left would be largely spent by the survivors on importing desperately food and equipment, which again would boost jobs and demand in the US. The loss of industry in the devastated region would mean reduced consumption of oil, lowering the world price per barrel.
In short, are catastrophes hell for those who suffer them, a windfall for the bystanders?