Wonder what the reference database was? In this situation, I'm guessing US immigration via either direct photography if entry via a manual immigration officer, or your saved passport photo when scanned on entry (would be a bit crummy, you'd think). Other?
If so, the airline is using a USA identification database for its operations. I guess they could manage it such that it is the airport (US Govt) using its own database and supplying a 'service' to the airline.
Any other info on how it works at, say LAX?