Earlier quoted context omitted.
Not direct malice, but naive over-optimism gone a little too far, perhaps. Krugman has written and spoken a lot about this in a way that's accessible to the interested layman. Search for "krugman optimal currency area", or see https://krugman.blogs.nytimes.com/2012/06/24/revenge-of-the-... . The point is that there are definitely economic benefits to the simplicity and low-overhead of currency union among equal and n…
>> The point is that there are definitely economic benefits to the simplicity and low-overhead of currency union among equal and near-equal partners, but when economic conditions vary greatly between regions (or more correctly, when economic conditions change differently over time in various regions), there can be a greater benefit to having different currencies that can trade at different levels against each other t…
By being one country as well as one currency region.
That's not just a glib answer. The US can use federal financial transfers to help, say, Mississippi. But the EU can't use direct financial transfers to help Greece, because EU rules (IIUC) don't allow it, and Germany (for example) wouldn't put up with being taxed to pay for it even if the rules allowed it.