America Samoa also has its own representation in the Olympics. Gibraltar does not, and is part of the UK as well as using ECF rating.
It should be noted that there is enough travel between Scotland, Wales, Ireland, and England that use of the ECF ratings is not a big surprise. Historically those countries were part of the UK for a long time, and thus used England’s rating system. Unless one of those countries wanted to use FIDE ratings, it made no sense to develop their own system rather than use the ECF system. Do remember that less than 40 years ago there were no FIDE ratings under 1800.
Wasn’t there a time when FIDE ratings below 2205 were kept internally but not published?
One has to wonder how much of the difference between US Chess and FIDE ratings is due to deflationary factors that FIDE does not deal with but US Chess does.
I believe the President of that Federation lives part of the year in New Hampshire. You can probably easily make contact to see what is required to be considered. I think they hosted a continental event last year.