I say this on account that unlike China which was dealing with about two centuries of decline before fully falling into civil war, this US civil war would be far more immediate and far more devastating not just to the US but to the entire world since they will be dealing with millions of refugees not just from the US but from all over the world as the worlds largest economy and agriculture producer falls apart.
Really what I am saying is that if the US falls like most 21st century Second Civil War scenarios have it fall, the consequences would be far worse than they usually occur in said scenarios.
Really I would say it would be closer to the fall o Rome than China.
America is practically the fulcrum of the current global system, and has been that for roughly a century.
Since the cataclysm of WWI, the American government's choices have always had broader global ramifications. In the 1920s, America's decision to cut off immigration, have an unregulated financial market, retreat back into isolationism, and do nothing about a crisis of overproduction contributed massively to the global Great Depression and the second major cataclysm of the 20th century.
After that, Americans leaders decided that their country must be involved in global affairs, for better or worse. Whether it was free trade agreements, CIA Coups, the International Criminal Court, or Botswanan kids watching Steven Spielberg movies, no nation in history has had such a global, all-encompassing, and powerful reach in world affairs as America.
A world with Pax Americana is the only one all humans have a memory of. If it comes to an end, either due to an American Civil War or an American retreat, the entire world would have to rewrite its rules and expectations of what is normal or not.