Not Only the EU but the USA Should have More than One Currency

I quote Arnold Kling about a quote of Paul  Krugman

The quote:

fiat currencies have underlying value because men with guns say they do.

Don’t peek at the answer, which is below the fold.
Hint 1: You may have read the essay by following a link from Marginal Revolution (but I came across the essay earlier from a different link).
Hint 2: I find much to agree with in the essay.

The writer is not otherwise known for libertarian dog-whistling.

Before I looked I guessed an MMTer like Simon Wren-Lewis.

But I agree with Paul Krugman that this is not a problem. On the other hand I think competitive private currencies (also) would be more stable. The problem that I see is people in developed countries  trust Government currency to much and so horde it in a down turn exacerbating the problem, making it so when one bank fails rather than strengthening competing banks it weakens them.

I also think the USA and the EU are too big to each have a single currency. That is because mismanagement by a single central bank, like in 2008 can significantly, hurt the world economy too much. The USA could have 4 or five regional banks and currencies.