Catholic Church, the Whore of Babylon
Judging by the criteria of biblical fundamentalism (literal words literally understood) it is certain that there is no mention of the Catholic Church in the book of Revelation as the Whore of Babylon. By contortions of interpretation (not biblical literalism) some groups and individuals equate the Whore in Revelation 17:9 with the Catholic Church since Rome is the famous city of seven hills and the Church's principal See is Rome. This position is untenable, both factually and from the only words of Scripture which tell us of the actual doctrine of the Antichrist, those of the apostle John in his letters.
There would seem to be two choices, either interpret Rev 17:9 absolutely literally or according to some interpretive key that is metaphorical, allegorical or otherwise non-literal. Lets look first at literal interpretation.
"The seven heads represent seven hills on which the woman sits." First of all, no Pope has ever lived or had his "seat" (cathedra or cathedral) on any of the seven hills of Rome. These hills are small hillocks (Capitoline, Palatine, Esquiline, Aventine and three lesser "bumps" in central Rome) where the religion and government of pagan Rome was situated. The Catholic Church's headquarters at the Lateran (the cathedral) and at the Vatican (where the Pope lives) does not coincide with them. At the time that John wrote Revelation the Christians of Rome lived mostly in Trastevere (trans Tiber), a district "across the Tiber" from the City and adjacent to the Vatican hill where St. Peter was crucified and buried. The Vatican is on top of that burial site and is today its own city-state distinct from Rome and Italy.
So, of what was St. John speaking when he wrote Revelation on the island of Patmos around 96 AD? Obviously of the pagan imperial system situated on the Seven Hills, especially the Capitoline (the religious and political center) and the Palatine (the imperial palace). This pagan power persecuted the Church of Rome in Nero's day (64-67 AD), and in the mid-90s under Domitian was persecuting Christians throughout the Roman world. Domitian was considered by the people a re-incarnation of the evil, but well-liked, Nero (the head that lives again). While the antichrist Nero persecuted only the Christians of Rome, Domitian extended that persecution throughout the empire. Both are thus types of the final persecutor, the Antichrist.
Why the cryptic name Babylon? First, the historical Babylon was the pagan power which persecuted the People of God, the Jews, between 610 and 538 BC, destroying the Temple and dispersing the people. The Romans inherited that mantle of infamy when they destroyed the Temple in 70 AD, and, more importantly, persecuted the new People of God, the Church. Thus, St. Peter, writing from Rome refers to as "Babylon" (1 Pt. 5:13) - a name any Jew or Christian familiar with the Old Testament would know.
How does this relate to the Antichrist? The future Antichrist will be a world-wide power, essentially pagan, which will persecute the Catholic Church (and orthodox Christians in general) everywhere, as the Babylonians persecuted the Jews and 1st century Rome the Church. These are biblical types! The Babylon of John's day, Rome, stands for the kingdom of the future Antichrist and is no more likely to be situated in Italy than Rome needed to be situated in Babylonia (modern Iraq). John was informing his readers of these prophetic types by drawing their attention to the contemporary fulfillment they found in pagan Rome. The Antichrist will come out of the Christian world (Greco-Roman civilization) to be sure (1 John 2:19), but America is as much an inheritor of that civilization as Europe and just as likely to be the source of the Antichrist.
Finally, after distorting the text and history to read what they want into the Bible, and thereby obtaining God's "blessing" on their hatred of the Catholic Church, some "Christians" ignore the only texts of Scripture which tells us about the religious leanings of the Antichrist. The Catholic faith being a religion you would think they would see what it teaches on the only criteria the Bible actually gives about the Antichrist. In St. John's letters (1 John 4, 2 John 1), he tells us that the spirit of the Antichrist denies the Incarnation (the Son of God becoming man) and thereby also the Trinity (the Father and the Spirit, too). This is the spirit of the Antichrist. There is not a single text in 2000 years, including the new Catechism of the Catholic Church, where the Catholic Church, her popes, her bishops, her official teachings, her saints, or her acknowledged ecclesiastical authors, deny the Word-made-flesh or the Blessed Trinity. Instead, all of Christianity owes the preservation of these Truths to the Catholic Church, whose great Councils formulated them and whose saints and popes have defended them to this day, often at the cost of martyrdom. The present pope, John Paul II, has written three great encyclical (circular) letters on the Trinity, one for each Divine Person, and he has without a doubt preached Jesus Christ to more people than any other person in human history. The Catholic Church does not have the spirit of the Antichrist but of God, since no one without the Spirit can say "Jesus is Lord" (1 Cor. 12:3), something the Church and Catholics always have done and continue to do!