This page:
https://www.facebook.com/AmeraucanaBreedersClub/is the official FB page for the Ameraucana Breeders Club.
There are many groups on FB, for discussion and for marketing, such as the Real Ameraucana Group and Real Ameraucana Marketplace, that are not "official" groups for any group, club, or other affiliation. The Real Ameraucana Group was started by Jean Ribbeck in 2013 and the Real Ameraucana Marketplace was added a bit later. The posted rules for both groups state they are not official representatives of any club, and club membership to any club is neither required or monitored.
From the pinned post of the rules in the Real Ameraucana group:
"Real Ameraucana Group - The Rules
SUSAN MOUW·TUESDAY, DECEMBER 6, 2016
1. This group is for the discussion of Ameraucana, and Ameraucana project varieties and is open to anyone that has, breeds, or wants Ameraucana. You do not need to be a member of any club, organization, or group."