Europe needs money for importing energy. This is a life-or-death sort of thing, given how cold it gets in some European countries. Europe also imports large amounts of electronics and machinery.
And they can't pay with their own currencies? If they import from other countries, that is?
> Europe also imports large amounts of electronics and machinery
From the US? Would their other vendors terribly mind taking Euros instead?
If they EU push hard for it, they may get someone like Norway to accept Euros.
However, there are energy contracts locked into dollar-based pricing and many exporters need dollars because they hold dollar-based debt, buy goods in dollars or have a currency peg.
For them to accept the relatively unappealing Euros they might ask for a premium to offset conversion costs or risks.
But that would be a monumental shift and the path to that goal is a nightmare with all kinds of challenges.
Rewiring the entire system would take a decade or more.