A lot of times, people ask why, if God exists, doesn't He show Himself? Why does he expect us to use faith instead of proving Himself by appearing on Main Street?
I think that the Bible actually answers this; according to the Bible, there is no reason for anyone to think that if God showed Himself, that people would believe.
Even if one looks at the story of Cain and Abel as myth, it is very clear that the people who wrote the story believed that someone could have direct contact with God and still reject Him.
Moereover, when the Israelites came out of Egypt, they saw many miraculous happenings, and yet still stopped believing whenever the going got tough.
Also, there were occurrences in the New Testament when Christ performed miracles, but people who believed the miracles were true still refused to believe He was Christ, because to do so would require too big a change in their world view.
So in short, I don't think that God suddenly performing an obvious miracle would necessarily have the effect of causing a sudden revival. In fact, it might even lead to people going en masse to some other faith if some people decided to twist the message.
I may think more about this later.
That is all.