[qwertox]

The issue is not having Europeans sharing photos and posts with Americans, but to have unshared personal data like logs, user preferences or non-public PII hosted on European servers without granting the US government access to it since it is outside of their jurisdiction.

Also, if a European citizen shares photos with an American friend, this friend will fetch the image from an European server, so that the US government doesn't have access to the remaining photos, unless they contact European authorities.