The Roman Catholic Church is comprised of 219,000 plus local parishes, whose churches are often in the same cities and towns as the assemblies of Protestants and Jews. It seems to me you do not know what Revelation 18 really means.
"It is within the city of Rome, called the city of seven hills, that the entire area of Vatican State proper is now confined." [The Catholic Encyclopedia (Thomas Nelson, 1976), s.v. "Rome."]
Seventh Day Adventists and others apparently use this quote and a Catholic forum has a thread contradicting it, including a scan of the old Catholic Encyclopedia. Have you actually read the quote in your version of the Catholic Encyclopedia ?
Your interpretation regarding the seven hills is flawed as the Christians in Rome were on the other side of the river. The seat of the Roman Empire was in Rome of seven hills.
Try to explain your technicalities to God not me.