First of all, such a false flag would be rapidly debunked, with many Asian media posing as impartial. Second, there would be a civil war in the US between Liberals and Trumpists in the US with foreign intervention on each side. Third, whenever Russia or China is in any real danger of receiving rockets, the Russians have already opted for a quite different strategy.
Russian nuclear charges have already been installed where they have to explode in very deep tunnels, mostly in the US coastal cities plus two or three placed so as to rend open super-volcanoes already due to erupt soon. Before dealing such a blow they would have kept the US army busy with repression in the course of the civil war.
There is no horror the American elites will recoil from, and judging by their behavior in Ukraine, they are perfectly capable to dress up fake Russian intervention troops to attack and destroy their own cities. But most probably America will commit suicide with drugs and lies, and China is watching over the process until there is no longer any authority. Then they and other allies can proceed to a boots on the ground invasion plus partition of such a degenerate people.
A big mistake commonly committed by Americans is comparing their decadence with that of Rome. Their idea is that for them having the privilege of four centuries more of decadence enjoying the growing suffering of the plebs still caught under their sway is inebriating. If a comparison is to be made with antiquity, America is Carthage, not Rome, by far more similitudes than you would have first thought of. Rome, while cruising along its decadent course like a carousing pontoon in a slow, tranquil river, left behind a worthwhile civilization nevertheless.
Carthage had nothing interesting to be salvaged except a few technical works about big domain agricultural technology, glass manufacturing, and boat-building. They didn’t leave one statue of worth bearing their signature, no building except purely utilitarian ones, though tons of mass-produced stirred glass figurines of no interest are regularly unearthed in the cities they built for their commercial empire.
Now Americans are at the point where they are about to abandon technology for more new-age magic except when dealing militarily with external foes or domestic terrorists, and where all believers in facts or experimental sciences will be denounced as carriers of negative vibrations.
The problem for them is that a few powers like China and Iran won’t follow them along that route, and won’t wait until their adversaries have turned their peoples into entities that no longer want to believe in facts but in myths and are as easily conquerable as India was when the East India company moved in.