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.
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.
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.
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.