I don't understand the meaning of the sentence. Although I got it right, I was not sure what it was supposed to mean - is the church building about to fall down; are church members losing faith, what? This is one of those sentences in Duolingo that makes me scratch my head. I can't imagine ever needing to say this in Spanish conversation.
I'm not a native speaker, but I am fluent and living in Central America; and I feel like this sentence would be understood both ways. Thus it could mean that the church building is physically going to collapse, or that the worldwide christian church is going to fail. It makes sense grammatically, but I don't see any situation where you would actually say this, except maybe as something they would shout at a pep rally for atheists.
You've raised a great question: Does "fall" have the same metaphorical meaning in Spanish (like in your "losing faith" example)? I wondered the same thing in this exercise, so I hope a native speaker will weigh in. Remember, it will only hinder learning a language to focus on what something doesn't teach you. I've never heard anyone actually say "See Spot run," in my whole life, but it seems to be the iconic sentence of English learning. Duolingo's model doesn't always lend itself well to explicit instruction, but that's what comments are for!
Because of the se, I understood it to be the church building itself, but then again, my indirect object/object pronouns study isn't quite as good as I'd like for it to be.
As for the statement in the sentence, collapse used to be a very common problem with old buildings that weren't maintained. They deteriorated over time until they eventually collapsed and fell down due to snow, wind, earthquake, or even their own weight. While it still happens occasionally even today, local building officials in many areas now have a tendency to step in and condemn such buildings before they get to that point!
I can't believe this sentence was added to the program. Everyone can have their own beliefs but making me type this sentence to proceed is evil. Jesus does not fail and at the second coming the author can explain if he meant the entire church or just a single building. May God have mercy on his soul.
I'm sure this MUST mean when you/I/whoever go into the church, it will fall down around you, being a comment more on the persons lack of normal attendance than the building/organization: it's a fairly common way to look at things in certain quarters and is NEVER meant to indicate that the church organization is going to collapse. I hope that eases the minds of the particularly religious members of this forum.