Now you mention it, despite the two respective national stereotypes, the only airports where I can remember seeing machine guns on the security team were one of the London airports.
If I saw machine guns in SFO or JFK, I was too tired from the flight to remember.
The dispatch time for armed police has gone up because they are doing a regular police job, while armed, rather than waiting for the call up.
Don't remember whether it was Incheon or Gimpo.
What I see now is occasional police officers with their standard sidearms, but rarely see anyone more armed than that.
Whereas in the US, every cop is armed but there's more checks on the more strict stuff.
Your airport police want to be armed but there's no need for them to be heavily armed. So in the UK they all are, because it's the same people. In the US the heavily armed folk are deployed elsewhere (SWATing someone's Twitch stream if the media tells me the truth...)
The war on terror really drove people crazy...
The "answers" the US came up with rather exacerbated the problem. Most also don't work with homegrown terrorism at all.
Using AI to profile such potential endemic perpetrators is ironically just another instance of trying to fit the problem to the tool.