I have never been a part of AMA, up here we have MAAC.
They are very helpful as well - but the best thing the AMA for me was the Model Aviation magazine.
I have no idea why anyone complains about it: I have read and re-read every issue from 1978 to 1984, aquired in a box at a library sale. It is great! Because of these issues, I learned almost all I knew before learning to fly myself. Most importantly, the Magazine, along with similarily dated RCM&E, enthused me enough to pursue this hobby!

Granted, the info was way outdated, no ARF's, computer radios, etc, but it taught me about building, free flight, and control line, all aspects of the hobby I would have not been exposed to today, which is unfortunate.

Thank you AMA!