Then I'll ask you the simple question: Is this universe the only one
Maybe.
It's a simple answer, the fact of the matter is that no one knows if this is the only universe. Though without any way to confirm the existence or absence of other universes, I just work under the assumption that there aren't any.
Let me ask you a question: Why do you only feel powerless when finding out that there is more than one universe, despite standing on a tiny blue ball orbiting one of the 300,000,000,000 stars in out galaxy, in only one of the 100,000,000,000 galaxies in the known universe?