I'm from the US but I lived in Argentina for about 5 years (2013-2018). It was a great lesson, and I'm seeing things in the US now that I used to see in Argentina. At the bank recently, they had a sign about the national shortage of coins. That was common in Argentina. Sizes of products getting smaller in order to keep the price the same - "inflacion escondido" (hidden inflation).
The ostensible reason for the coin shortage was COVID-related supply chains. Stores were also trying to minimize handling of cash especially early-on in the pandemic.
This is overlaid with the fact that, in the US:
1. A lot of people (though certainly not everyone) don't use a lot of cash these days
2. Coin denominations have basically been unchanged since I was born--which was... not recently. So you have lower denomination coins that cost more to make than they're worth.
In some cases, that may be technically true but I suspect that the costs of turning bags of pennies into cash that is > than the face value of the pennies is iffy at best.
The single greatest difference between the United States and Argentina is the world's debts, as tracked by the IMF, aren't denominated in any of the pesos or peso variants Argentina has used over the past several decades.
Were the us to try and trade out dollars for NuDollars, they would find the dollar won't go away because the world will still be using it to trade and pay down its debts.
The dollar being the world's international trade currency has a significant anchoring effect that makes it extremely difficult to extrapolate from lessons learned in other countries to the United States.
If the US decides to replace 10 Dollars with 1 NuDollars, then the IMF and everyone else will just search and replace and fix all the paperwork. It's not hard at all.
The problem may be if there is for many years a high unpredictable inflation that is higher than most developed countries. In that case other countries may decide to use Euros, Swiss Franc, Yuanes, Yens or whatever has a more stable value.
There's nothing in international law that makes that automatic.
It would create an interesting open question how the IMF would respond. In practice, it won't happen because raising the question would (as you noted) bea colossally stupid move for the US for global influence reasons. They have a lot of leverage from being the printer of the world's currency-of-record.
