We didn't have to show the attestation form at all. The email that AA sent us stated that if we hadn't filled it out, we would not be able to get our boarding passes. After we filled it out online, we were able to check in online, and get our boarding passes on our phones. The boarding passes were all that we needed to enter passport control and security. We don't check bags, so went directly to the check-in lines. It's completely pointless, but not difficult to manage.