Let me add another comment. NT Wright (who I know carries some weight around here) seems inclined in the direction of the view that harlot Babylon= Jerusalem. Here is something I wrote on this:

Interestingly, Wright noted that some scholars are actually hostile to anyone who says the harlot is not Rome. He wrote,

Recent commentators (e.g. Massyngberde Ford, 1975) have suggested the great and wicked city [of Rev. 17-19] is not Rome but Jerusalem (cf. Rev. 11:8). I have discovered that this suggestion arouses anger in some circles, which is not explained simply as annoyance at an exegetical peculiarity (plenty of those are to be found in all the journals, but they merely arouse curiosity). What is at stake here, and for whom?

N.T. Wright, Jesus and the Victory of God, Christian Origins and the Question of God, vol. 2 (Minneapolis: Fortress Press, 1996), footnote, 358.

Saying the harlot is unfaithful Israel should not be seen as an exegetical peculiarity. It is hardly a tangent driven by the quest for novel interpretation. Given the consistent OT portrayal of God’s unfaithful old covenant people as the harlot (Lev 17:7; Lev 20:5-6; Num 14:33; Num 15:39; Deut 31:16; Judg 2:17; Judg 8:27; 1 Chr. 5:25; 2 Chr 21:11; Ps 73:27; Hosea 1:2; Hos 2:2-5; Hos 4:15; Hos 9:1; Jer. 2:20; Jer 3:2,9,13: Jer 5:7,11; Jer 13:27; Eze. 6:9; Eze 16; Eze 23; Eze 43:7,9), unfaithful Israel should be the starting point in one’s examination of the harlot (click on some of those references for a quick overview on the harlot motif). There are only two exceptions (where a Gentile city is called a harlot) in the whole OT for goodness sake!

One of the conclusions that Wright came to in his study of the gospels is the following:

When we read through the synoptic tradition (and John, for that matter) we find a great deal of warning of coming judgment, in all strands of the traditions, and all pointing in one direction. Jesus, I shall now argue, predicted that judgment would fall on the nation [of Israel] in general and on Jerusalem in particular. That is to say, he reinterprets a standard Jewish belief (the coming judgment which would fall on the nations) in terms of a coming judgment which would fall on impenitent Israel. The great prophets had done exactly the same. Jerusalem, under its present regime, had become Babylon.

emphasis mine, Jesus and the Victory of God, 322-323

Wright further noted that his conclusion “may be held by some to carry implications for the reading of Rev. 17-19.” ibid 358

Wright is saying that if Jesus is borrowing from the language of the fall of Bablyon in talking about the fall of Jerusalem (Matthew 24:29 cf. Is. 13:10, 13) it should not be surprising that John is doing the same thing in Revelation.