J.M.
The AMA is just a club. It's a big club. (It's the largest medical association in the country.) And it's a club with a lot of political clout, but it's only a club. ANYONE who is a doctor can join as far as I know. And membership doesn't mean a thing with regard to a doctor's skill. The primary function of the AMA involves political efforts. If they are anything like the ABA, they also provide training, etc. for medical professionals and members of the AMA get a discount for taking their training. My guess is that the AMA also provides some advertising for and credibility to their members.
The analog for lawyers is the ABA (American Bar Association). I'm required to be a member of the Washington Bar Association to practice law in this state, but membership in the ABA would NOT give me a license to practice anywhere in America. (I would have to become a member of each individual state.) Although the ABA is the largest organization (club) in the world and is VERY well known, membership in the ABA does not mean anything except that someone is a licensed attorney who paid a fee to join the ABA club! (So even the absolute WORST lawyers can join without any problem!) I am not a member of the ABA because I don't want/need the advertising and I don't want to pay the dues, etc. I do enroll in some of the classes offered by the ABA, but I just pay full price. Neither my legal practice nor my professional reputation is harmed in any way by my decision not to join the ABA (and I may very well join at some point in the future . . . but it darn sure won't be before my kidlets are grown!).
Good luck with your surgery! Board certification and a positive recommendation by a former patient means a heckuva lot more than being a member of the AMA!