Speaking as an N-reg aircraft owner, UK AOPA did not do themselves any favours with a large number of owner pilots by their very ambivalent stance on the N-reg issue over the years.
At one point it got so bad that somebody did a Freedom of Information Act request on the CAA to try to get copies of correspondence, IIRC, between them and AOPA.
I think this may be in the past now, looking at recent UK AOPA statements on the stupidity of the EASA proposals, but it has taken them an awfully long time.
Like it or not, this kind of thing sticks for a long time, and the apparent reason for it (a large number of flying schools, traditionally anti N-reg, are AOPA corporate members) has not changed.
I am a member of US AOPA
I believe that to be false. AOPA were actively opposing N-reg restrictions in the UK as long ago (IIRC) 2004. That's at least 7 years of consistent pro-N work. How long can one hold a grudge? I don't even believe there is any substance to that grudge. Give me one example, EVER, of AOPA being anti N-reg?
The problem for AOPA is the cluelessness of the community of pilots in Europe who expect tiny voluntary organisations to be like big commercial enterprises, vigorously competing for their membership. Sort of like mobile companies endlessly trying to sell you your perfect membership plan, with the perfect balance of people representing exactly the things you are interested in, in exactly the style you want and with every interaction and communication meeting your high expectations. Well, it ain't like that. They are small voluntary organisations, with all the imperfections inherent in that, in the big European countries. Even tinier in the small countries. Nevertheless, the critical battles are often at a European level, and every national AOPA and every last member helps that.
Forgive my bluntness. I generally despair about the over-regulated, over-taxed, over-restricted misery of European GA. When I read some of the ways people think about (not) supporting the representative organisations (and compare that to the US), I think we
deserve it.