Maybe someone can clear this up; when I get into the US on vacation, my fingerprints and iris are stored. Then when I walk from the plane to customs there are a

Maybe someone can clear this up; when I get into the US on vacation, my fingerprints and iris are stored. Then when I walk from the plane to customs there are a ton of cameras, they scan my passport (which has biometric info and my photo), then they take a photo of me. This is not the same for citizens? I would imagine it would be quite easy to figure out who is who with all that info? If Americans never fly, do they not have biometrics on these people?