It's easy to see a world where the US dollar is 40% devalued (such would be logical, and should have happened, bar domestic Chinese and other South East Asian policies, which prefer to hold down their domestic currencies by holding USD assets).

But a really big devaluation beyond that, when roughly half the world's economy is denominated in dollars, is hard to see.

Also Europe is in a relatively worse position in a PO scenario.  Yes we consume less, but we import 80% of our energy (coal mines in eastern Europe, and some renewables, plus of course the North Sea, but that is about it).

The US by contrast is the world's largest or second largest coal producer. Plus it has access to Canadian tar sands, Arctic gas etc.  And it has big biomass resources (wood for heating etc.).

Another factor (the same for CO2 emissions) is that the US would find it relatively easy to reduce energy consumption-- simply switching to diesel powered cars, ditching SUVs etc.  By and large, Europe has already made those sacrifices.

Eventually Italy will find a way to exit, and Greece also-- both countries are effectively having their economies strangled by deflation.

I don't think many of the EU25 countries that are not in the Euro (UK, Denmark, Hungary, Poland etc.) are likely to rush to join it-- the ones who would benefit (Hungary) are precisely the ones in the worst fiscal position and break the ECB rules.

The euro will revert to what it always was: a Franco-German currency union, with Benelux (and maybe the Irish and the Spanish) along for the ride.