Whoa. Downvotes ...
As if world power had something to do with technicalities, IT-systems, which currency to transact in.
Sorry guys. This is not how the world works.
The USD is dominant currency not because of the lack of alternatives.
The USD is the dominant currency because USA is the dominant military power by an order of magnitude.
As long as that is the case it means the EU can get only token independence. Ultimately if the US says no - you cannot deal with Iran. Then that is the way it is.
Does it mean that the EU is going to be nuclear bombed by the US? Of course not. It is much cheaper to go: One of your banks. It is not allowed to trade in USD anymore.