I never think of religion as being too predominant in The Glass Menagerie. There are definitely some references - mainly to Catholicism - but they tend to be ironic and subsumed to the larger themes of escape, art and individuality. In the 1930's America, religion would have played a large part in identity, and Amanda seems to hold to her Catholic persona pretty strongly, but it's just one of her many delusions. I think Tom would see this devotion to Church as yet another of the many delusions that trap him in this family. Tom ultimately makes the agonizing decision to run away like his father did, leaving his sister alone, all for the sake of following his own calling. Religion is one of the things he is repudiating in order to live a life of an artist, though again, I don't consider it a major theme in the work.