The sigh of the oppressed creature, the heart of a heartless world.....
So, while institution is the correct sociological word, in common parlance the word institution tends to refer to be thought of as something more organized. It's not quite as organized as all that. Indeed, it's much more subtle and, I think, insidious because they're appealing to the energies the left normally appeals to! They offer folks what they need--an antidote to alienation--and a sense of belonging to something and sense of efficacy even if only a sense of efficacy within one's rather small community of faith, family, friends, neighborhood."
Oh, I totally agree, religious space is the last social space left in the U.S.; it's the last form of "community" offered/available. But, as you note in the last paragraph, the move to religious grouplets is inadequate to the problem. It solves neither the religious problem (which cannot be solved through the creation of a bubble of a safe heaven, through escape from the real) nor does it solve the social problem, which must be solved in social terms and solved universally.
Joanna