The US recovered due to the war being short and there being a full Northern victory for reunification, with the north increasing its industrial capacity in the process. Industrial capacity was leveraged to create systems of unequal exchange in America's new colonies, particularly the Philippines and much of Latin America.

We live under neoliberal capitalism where industrial capacity is already developed in other countries and they wouldn't just wait for the US to reunite, if it ever did. They would construct their own systems at the expense of the US order. The empire would be headless and the entire rest of the planet would act accordingly. Sure, the former US would still make weapons, weapons to kill each other with while they blow through stockpiles and can no longer afford imported materials. But the US isn't going to reindustrialize in five years, it has already lost industrial advantage, it only has financial and military power that would be thrown into internal chaos.

The rest of the world would reel from the collapse of the US, trying to find footing with the loss of the current order. Financial systems, food systems, energy would all change overnight. They'd build their own alternatives out of necessity and that means building alternate power structures. Everything would get worse (for years) but the balance would change.