There is a USAF investigation ongoing into the breach of security on the C-17A that clearly either didn't have attached AT Sy or it was inadequate. Not only did 640 people storm aboard but some of them did it while the aircraft was taxying with the rear ramp still partly open. Personally I found that strange when USAF Security Forces is the largest career field with over 55,000 personnel.
Somewhere between 10,000 and 15,000 US citizens are stranded in Kabul - most of them not at the airport.
By comparison, here are a couple of videos of the way the UK handled UK citizens and entitled Afghans - AT Sy on each aircraft and orderly loading: