Q. Is a Jew who is alcoholic permitted to enter a church (even possibly the main sanctuary) to attend an AA meeting?
A. It is forbidden to enter a house of avodah zarah or a church. (Y.D. 150,1- 157,3 – Shach ibid. 149,1.) R’ Moshe Feinstein Zt"l (Igros Moshe O.C. 4,40,26) prohibits students playing ball in a sports hall that belongs to a church, even if no religious images are present. (See Rivavos Ephraim 3, 302,3)
However Poskim do permit voting in a locale adjoining or connected to a church, which specifically set up a venue for that purpose and it is marked or is known to be so. This sanction is only ex post facto, when no other voting location was made available or is found close by. (Teshuvos Vehanchogos 2,410).
Horav Shlomo Miller Shlit"a permits using the A.A. church venue, if the meetings are not held in the sanctuary, and it is clearly identified or known as a setting for social or community activities.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit"a