Having not studied economics/politics during my time in college, wow does one qualify "collapse" here? What are the properties?
Such a collapse would bring China back to the 1980s, increase poverty by hundreds of millions of people, disrupt global supply Chains (50% of the global electronics are shipped from the Pearl River Delta, 50% of all ACs and fridges are made there, Daimler, BMW and GM source 20-30% of their parts from China).
Western factories would reduce production as parts are missing. Western companies that export to China would have to reduce output (Volkswagen, GM would have to cut production by 30-40%, Airbus and Boeing by 20-30%). Western stock markets plummet, housing crises emerge, poverty surges, unemployment increases dramatically.
All in all, this would not be a great thing and a lose-lose situation. The Soviet Union was not integrated into the global value chains. China is. A collapse would make the 2008 crisis look like a cute little girl on a pink bicycle and bring the global economies back into the 1990s.
War is chaos. War destroys supply chains. War is standing in direct contrast to planability.
Nobody wants war.
Just look at Russia and its behaviour after the collapse of the Soviet Union. 1991-2000 was pure shit: chaos, corruption, high suicide rates, absolute poverty where poor old Grandmas and Grandpas suffered and committed suicide as there was absolutely nothing. In the early 2000s reforms were made that brought certain stability back to the country. Unfortunately, the economy was depending on resource exploitation - and the government knew that ofc. They tried to open up and integrate themselves into the global economy, e.g. by suggestion to join the NATO (for more stability and less spending on the military) and to join the EU (for better integration into the European markets). The Western nations said no to both suggestions. This is where the wars began: Georgia, North Kaukasus, Ukraine and now Syria.
My two cents: it was a huge bullshit made by the USA to 1) fuck the ex Soviet republics after the collapse in 91 - and yes, they had the option for a Marshall plan 2, and 2) to not integrate Russia into the Western military and economy. Shit for Russia, shit for the EU, shit for the US, shit for the global economy. Thanks again, USA.
Recovery wouldn't happen immediately but there are a lot of towns and cities with shuttered factories, particularly in the Rust Belt and the Northeast which I could see revitalized. Increased manufacturing would vastly increase the economic diversity of the country, instead of a situation where most jobs that pay a living wage are concentrated in few cities and few industries. A diverse economy would vastly improve the housing situation, since there is abundant land and housing in the middle of the country. It would also do wonders for halting Climate Change, since the US has much cleaner power, transportation, and emissions regulations.