Iran considers itself in a state of war with the U.S. and will as long as the billionaire clerics run the country.
Since the U.S. doesn’t buy their oil anyway and isn’t likely to do it, it’s not going to cause the U.S. companies to have to buy Euros. Seems to me it’s just a gesture of defiance, like “death to America” chants. But it might haunt them eventually. All currency has to eventually return to its country of origin in some manner. It might be in the form of buying products. It might be in the form of investment. It might be in the form of financial assets. It might be land. It might even be deposits in banks.
So, Iran’s Euros will have to return to the Eurozone at some point. Maybe Iran will find everything it wants to buy there, and maybe it won’t. Maybe the prices will be more favorable, and maybe not. Right now, interest rates in the Eurozone are negative. Its markets are down worse than ours. Real estate isn’t a good investment in a falling population. And there’s not a whole lot of food for export in Europe. There are a lot of countries that will take Euros or dollars, but insisting on dealing in Euros is going to limit Iran’s trade, at least somewhat.
So, if Iran really wants to “partially sanction” itself, I say let it.