I'm from Massachusetts (Cape Cod) - maybe my observations would add something useful. I believe it's as you say - acquired immunity.

Most restrictions are all but gone- state offices still require a mask, but everything else appears to be voluntary and/or the discretion of local counties and towns. I think kids are still forced to wear them in at least some schools. For the most part, everywhere you go there are no restrictions at all, apart from sometimes a sign asking unvaxxed people to wear a mask, but nobody really cares or pays any attention to it. This is virtually all stores, banks, libraries and restaurants. Of course, I have not submitted to the shots, but I go most everywhere freely and though I guess (from the stats) most people are vaxxed, hardly anyone seems worried about it anymore. Some people still wear masks when they don't have to, but they're a minority now.

It was a busy tourist season this year, with lots of people from everywhere mixing quite freely. Even 2020- the height of the lockdowns- tourists were here and we were all mixing pretty casually, shaking hands and all that.

The only person I know who's had any flu/covid or whatever this year was fully vaxxed. I believe there are a lot of vaxxed people who have some regrets. But, regrets or not, most vaxxed people I've encountered do not seem worried about the vax status of others.

Take my observations for whatever they're worth. I'm speaking only from what I've seen myself and what other people around here have told me.