Sorry, do you mean Manchester, New Hampshire? MHT/KMHT? Good grief man.......
As it happens, I have flown through MHT/KMHT. I can't recall what their security arrangements were like ... it must have been quickly forgotten as a very average experience!
I know a skewed data point when I see one.
Based upon what you have written, the jury is out on that one!
No wonder none of the US carriers will touch it any more.
The Transatlantic carriers have retrenched from the regions (and LGW) to LHR in order to protect their slot banks there until business rebuilds to approach and reliably sustain pre-pandemic levels. They have not left MAN due to dissatisfaction with the airport experience, and they enjoyed very healthy customer demand here too. That's why United Airlines looks good for a return once normality is restored to Transatlantic travel flows. Delta Air Lines would point out that their partnership with Virgin Atlantic represents their MAN presence (Virgin too have suspended a number of regional services including some from MAN to concentrate on safeguarding LHR slots). Oneworld is now represented at MAN by the new Aer Lingus Transatlantic base ... this has allowed American Airlines to likewise concentrate on protecting high-value slot assets at LHR. As for up-and-coming US carriers ... they're already known to be checking out the proposition offered by MAN. Watch this space?
It is a little bit naughty to conflate your personal distaste for MAN with a suggestion that all US carriers have exited MAN during the biggest pandemic in the history of the industry because they have an issue with the airport's passenger experience!