Here's my take:
There are seven kings. But five has fallen.
Five fallen kings represents the most powerful empire in history.
1) The Persian Empire
2) The Roman Empire
3) The Caliphate
4) The Mongol Empire
5) The British Empire
Ref:
5 Fallen Kings
Kings coming soon:
6) The False Prophet (2nd beast)
7) The False Christ (1st beast)
8) The Serpent who belongs to the 7th King for they are one -- the false Christ is Satan incarnate.
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The Ten Horns - They are the ten Presidents / Prime Ministers / Kings from the powerful nations on earth. Perhaps, USA, Canada, Russia, China, Japan, Great Britain, Germany, Saudi Arabia, Italy, and France.
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“The waters you saw, where the prostitute sits, are peoples, multitudes, nations and languages." -- This could be Christianity that has fallen away (apostasy) to take the mark and worship the beast. Fallen Christianity became a prostitute. The beast and the ten horns will hate the prostitute and will destroy her.
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"The woman you saw is the great city that rules over the kings of the earth.” -- This could be Washington D.C., the seat of power of the most powerful nation on earth - The United States of America.
That's it for now.