GDPR applies to anyone processing personal data about a subject who is in the EU. His or her citizenship does not matter. So you can just go to Europe and make your claim from there. https://gdpr-info.eu/art-3-gdpr/
It may be - but that would just allow Facebook to say "if the login is from an EU IP, don't save this record" - but the rest of your profile, generated in the United States, can still remain. As long as no collection happens while you're within the EU, they may be fine. The whole thing will have to play itself out in court, it seems.
