Russia-USA war would probably improve economic growth... Net positivity, maybe not.
a Russia-USA war would improve the economy of China. It will destroy the economies of both Russia and the United States. Remember the WW2. The US emerged as a world power after
WW2 WW1, because it limited its participation in the battle for the initial 3-4 years.
Another correction made!
The USA had been heavily crediting its allies during WW1 and earned a heap of money and power (read John Keynes' work "The Economic Consequences of the Peace" if you are curious)...