The entire World is going to experience a major wake up.....I regret to say, there is only one outcome of all of this.....taint gonna be pretty.
But if the world does enter a new era of barbarism, we will be the first ones out of it for a number of reasons:
There are still a number of Americans who remember what self-reliance is like. They will form farms and defensible areas in a still very productive Midwest.
The Europeans will return to fighting amongst themselves: French against Germans against Brits, etc.
The Chinese will retrench behind the great wall and their history of self-sacrifice and self-abnegation - besides, they have a rapidly depopulating Russian Siberia right at their doorsteps to plunder if necessary.
Lastly, the Muslim Arabs will immediately sink back into the nomad sands with no one to buy their oil - they lack even the rudiments of science, agriculture or even culture for that matter to keep them together if the fit hits hits the shan.
Yes, it will be bad. But the US (with Australia and maybe New Zealand) are best equipped to deal with the coming apocalypse.
Certainly something never predicted by Keynes or the Keynesians.