What if a revolution in the US caused a global economic collapse?
We tend to think of potential revolutions in the same way as the US Civil War, or the French or Russian revolutions. The problem is that a civil war would be much more like the British Civil War, and most people know very little about the French or Russian revolutions.
A Revolution or Civil war wouldn't have 2 times. It'd have a dozen. We can't agree on what the future of the country should be now, how would we in a Revolution? There would be Revolution, counter-revolution, a civil war where the sides shift every 6 months. And you know how other countries try to influence us now, with Russia interfering with elections and China manipulating companies? That's with the full strength of the Federal government attempting to stop it. Now they'd get to do it with an extremely vulnerable, fractured country.
Add on to that that those other revolutions involved world powers, but in a far less connected world wide economy. The fall of the US looks less like the French Revolution, and more like the Bronze Age collapse.
I think it's too soon to write off the US as irredeemable without revolution. The last time we had a brush with Fascism taking over the country, we got FDR and The New Deal. If we can avoid this brush with Fascism, we might get another chance at turning things around.