But even that is only as good as the infrastructure behind it. I landed at Dulles on an international flight one day and the entire immigration system was down

But even that is only as good as the infrastructure behind it. I landed at Dulles on an international flight one day and the entire immigration system was down so none of the self-service kiosks or agent terminals were working creating huge backlogs. In the end US passport holders were let through with a visual passport check while all others were SOL until the system came back online.