@John *********
Passport details aren't shared as much as you think. The US want to know more about people coming to the US than the other way around. Any country wishing to participate in the US Waiver Scheme has to collect data to US standards. UK passports do not meet EU standards because fingerprints aren't shared. When your passport is scanned, it's checking that the basic data matches what's printed on the passport. This is why dodgy people end up in Thailand on stolen passports. The data isn't even flagging a stolen passport. The US State Department will maintain records on its citizens linked to God knows what databases, but there is no way an IO at BKK will be able to access US government databases.