Answering a question on r/askeconomics got me pointed in the direction of Michael Pettis's writings on the reserve currency and the US trade deficits, and thus some bad economics. E.g.he quotes, approvingly, Jared Bernstein saying that:

If trade-surplus countries suppress their own consumption and use their excess savings to accumulate dollars, trade-deficit countries must absorb those excess savings to finance their excess consumption or investment.

But that's assigning an inappropriate causality to a transaction. Let's say today I bought a loaf of bread. Now that was conditional on there being a baker willing to sell me a loaf of bread. But it also was conditional on me wanting to buy a loaf of bread. No one is forced to bake bread. Both of us had to be willing to trade for the bread sale to happen.

Similarly, if some countries choose to suppress their own consumption, they can only accumulate US dollars if the US chooses to absorb those excess savings as consumption or investment.

And again:

The fact is that if foreign central banks buy trillions of dollars of US government bonds except in the very unlikely case that there just happen to be trillions of dollars of productive American investments whose backers were unable to proceed only because American financial markets were unable to provide capital at reasonable prices, then either the US savings rates had to drop because a speculative investment boom unleashed a debt-funded consumption boom (i.e. household consumption rose faster than household income) or the US savings rate had to drop because of a rise in American unemployment.

But of course, there's no reason that the US had to create trillions of dollars of US government bonds for foreigners to buy. If the US government only created billions of US dollar bonds, those foreign central banks would all be competing against each other to buy them, driving up US bond prices and thus down yields until enough central banks decided it wasn't worth it and dropped out.

This is just a variant of Alfred Marshall's famous line:

We might as reasonably dispute, whether it is the upper or under blade of a pair of scissors that cuts a piece of paper, as whether value is governed by utility or cost of production.

It hardly seems worthwhile to give a source for this basic point, but rules are rules so here's an NBER paper by Barry Eichengreen on some of the history of reserve currencies.