Q. Is there any proof that Revelation talks about the United States (or that the book of Daniel does)?
Whether we see the United States (or any modern-day individuals, nations, or institutions) in the biblical apocalyptic books of Revelation and Daniel depends on the interpretive presuppositions we adopt as we approach these books. As I explain in my Daniel-Revelation study guide in the case of Revelation (similar things might be said about Daniel):
The book of Revelation is interpreted in four major ways. The futurist approach understands it to be a description of the events of the “end times,” at the end of human history. (Works like the novels and movies in the Left Behind series follow this approach.) The historicist view sees the book as a prediction of the whole course of history, from Jesus and the apostles down through the present to the end of the world. The idealist interpretation is that Revelation depicts the struggles and triumphs that followers of Jesus will experience everywhere, but it doesn’t have any particular place or time in view. The preterist approach is to try to understand the book by reference to the time and place it was written in–western Asia Minor towards the close of the first century.
I personally believe that a preterist approach is the most responsible one to take, as it is consistent with the way we approach every other book of the Bible, trying to understand it in light of its original historical and literary context. From that perspective, the characters and symbols in Revelation have directly in view the resumption of imperial persecution of Christians under Domitian in the late 80s or early 90s A.D. The visions in the book of Daniel, for their part, are initially envisioning the suffering of the Jews under Antiochus Epiphanes IV, who ruled from 175-164 B.C.
Applications to any other historical periods are secondary and need to be made by inference and analogy, although these biblical books can certainly inform us very effectively about what conditions are like, and what a faithful response should be, in comparable situations. Certainly those who are suffering for their testimony to Christ in our world today can and should find encouragement and challenge in many of the admonitions in the books of Daniel and Revelation, for example, “This calls for patient endurance on the part of the people of God who keep his commands and remain faithful to Jesus.”
I think we are better advised, in fact, to understand Daniel and Revelation as speaking to us today out of situations of persecution in the past, and so calling us to sympathy and solidarity with those who are suffering now, than we are to try to synchronize their characters and symbols with modern-day actors. That is a necessarily speculative exercise that may not lead to any response or action on our part.