You managed to miss the one case the grand parent poster actually mentioned: An EU person located in the US. This person is also covered by the GDPR thereby rendering any geo-absed rules and routings useless.
They are not, where are you getting this from?
Again, Article 3 from GDPR, "Territorial scope";
> 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
data subjects who are in the Union