The beast is a man and also an empire on earth he will rule.
The Harlot, is a false religion that will be destroyed by the beast.
I do not think the harlot is limited to any one religion.
All Praise The Ancient Of Days
The False Religion that most seems like a Harlot -- a Seduction to Evil -- is Paulism. Remember John was a lifelong Enemy of Paul. Every letter John wrote was rebuking Paul's doctrines of Free Sin. And in the front of the Book of Revelation, to the Church of Ephesus, John is congratulating the Ephesians for tossing Paul, the False Apostle out of town (and then Paul writes to Timothy complaining he was tossed out of Ephesus).
Look at Protestant/Paulist Doctrine, and the Doctrine of the Catholic Bishops (not the same doctrines as the Marian Religious Orders... certainly NOT). These Paulist Doctrines speak of a Religion that Forgives, that is ALLOWS Sin.
Think about it. A Religion whose primary selling point is that it FORGIVES SIN. Well, what more could Satan want?
Just think about it. Who stands to benefit the most from the forgiveness of Sin? Satan does. John, in one of his Letters clearly states this argument, that EVERY Demon BELIEVES in Jesus. If the Saving Blood of Jesus can get Sinners into Heaven, then what this spells out is the Victory of Satan over God, as the Worst Sinners will Overrun Heaven.
But only if what Paul said was true. But its not.
Who would be GOOFY enough to beleive that one can be SAVED by Killing Jesus.
Read the Parables. The parables speak of punishment for those who murder the Son of God. Not some HUGE REWARD for Murder.
Indeed, look at Jesus and his own attitude while he was being marched to his crucifixion. He was called down a Curse on Jerusalem.
Look at History since the Murder of Jesus. Does it LOOK like God was happy about it and decided to Forgive All Sins. Or does it rather look like God got really Pissed Off?