It makes sense for a German car manufacturer to pay taxes to Germany, since the German state provides it with services (roads, police, infrastructure.) It makes no sense for an American car manufacturer to pay taxes to Germany since it gets no services from Germany. (And no, earning the "privilege" of unloading the car from the boat isn't worth 20%.)
If the EU has an interest in making this fair, they can remit the sales tax they collected to the US government. Or they can just accept that this is a discriminatory tax and may incite another discriminatory tax on the US side.