So what do you make of the prediction from the Bible that “The Gates of Hell will not prevail against it.” (Church)?
Well, the simple answer is, as a non-believer, I don’t believe it! I’m not sure what else you were expecting me to say :)
But even if the bible quote is true, it’s true not just for the USA but for the whole world, most of which is already much less Christianized than America. So, even if we assume that your world view is correct, the future of America could easily be much more secular than it is today, by far. (In fact, many Christians are predicting that and much worse, given what they believe about the contents of Revelation.)