> This Regulation applies to the processing of personal data of data subjects who are in the Union by a controller or processor not established in the Union, where the processing activities are related to: the offering of goods or services, irrespective of whether a payment of the data subject is required, to such data subjects in the Union; or the monitoring of their behaviour as far as their behaviour takes place within the Union.
“offering of goods or services, irrespective of whether a payment of the data subject is required, to such data subjects in the Union; or the monitoring of their behaviour as far as their behaviour takes place within the Union.”
So Facebook US cannot divest itself as long as it serves customers in the EU or exchanges data about data subjects in the EU with its EU subsidiary.
You can read the actual text of the territorial scope rule here [1].
Edit: slightly less rough, but still quite rough:
[1] https://gdpr-info.eu/art-3-gdpr/