If I understand this correctly, the question is not Facebook's advertising, targeting and so on, but rather the ownership and location of the servers where all that is executed.
The EU insists that such servers have to be located in Europe and owned by a Facebook subsidiary that's covered by European law, Facebook insists on transmitting the data to the US and executing the targeting on servers owned by a Facebook subsidiary covered by American law.
The EU insists that such servers have to be located in Europe and owned by a Facebook subsidiary that's covered by European law, Facebook insists on transmitting the data to the US and executing the targeting on servers owned by a Facebook subsidiary covered by American law.
This seems implausible.