The safest assumption would be that if your face has ever featured in a photo on Facebook, it already is in their database.

Last couple times over the border the officers have pointed a camera at me (travelling on US passport), so I assume my mug is in there. Seems completely routine and universal at airports now? I wonder if the original passport photo has similarly been scanned at this point.

Don't they take photo and collect fingerprints when crossing the border?