Uhh... I’ll bite. Why would the American passengers be the EASIEST to identify?
Where they check in, present their tickets & show their passports. I don’t know about other countries, but U.S. passports are scannable. Learned that at the U.S. side of the Canadian border. Yes, hadn’t had a new passport in years.
Seems to me that U.S. passengers’ names would be scanned & entered onto the manifest database more reliably than those of some other nations.
That’s all I’m saying.