And upon her forehead was a name written, MYSTERY, BABYLON THE GREAT, THE MOTHER OF HARLOTS AND ABOMINATIONS OF THE EARTH. [King James Version; the New International Version uses "prostitutes" instead of "harlots"].
The ultra-evangelicals (ranging from the Adventists to the ratbags) mostly claim that it's a reference to the Papacy. Check out Rooster's answer.
The "harlot" doesn't exist. It's like embodying some of Nostradamus's (or Edgar Cayce's) prophecies with a reality they don't deserve. There's lots of hyperbole in Revelation. Good fun but not to be taken seriously.
Goodness me! Next we'll have somebody saying that Putin is the reincarnation of that fiendish Siberian holy man, Grigori Rasputin. What nonsense! We all know that Donald Trump is Rasputin reborn.
"Two authors that have written about their concerns that the United States meets the prophetic qualifications of Babylon the Great are Michael Ross and John Price. Their works, Babylon the Great: Day of Destruction (2016) and The End of America (2013), respectively, find agreement in their analyses that America is."