As discussed in other threads - I see nothing that requires membership in the AMA in the bill.
They are talking about operating "within the programing" of a national based org to me does not infer required membership, rather recognizing the safety guidelines of the AMA and use those as a safe operating structure.
Essentially we are saying users who are doing this for fun or sport don't need the regulation the FAA is recommending.
This is what happens when law makers right stuff (with the help of their law degrees or lawyers). The wording is interesting.