Two symbols are used for America in Bible prophecy: A prostitute named "Babylon" and the Eagle's wings on the back of a Lion (the Lion being the symbol for England). (See notes at the end of chapter 2.)
In Daniel 7:4, the Eagle's wings are plucked, and the Lion (i.e. England) ceases to be a "beast" (or world empire) as a result. In Revelation 17:16-18, and all of Revelation 18, we read of the fall of Babylon, and how it affects the kings, merchants, and shipping companies of the world.
Remember, however, that the term "Babylon" not only refers to America. It is a symbol for all of the empires of man. And so the title will eventually pass on to the new centre of world economics, under the new world order.
The rise of a single world religion may or may not be assisted by the United Nations. Moves toward ecumenicalism have been underway for some time now; but disasters always have a way of bringing the masses back to thoughts of religion, and of bringing religious leaders together with one another.
America's obsession with Israel is usually explained to the masses (thanks to the churches) on the basis that they are God's "chosen people" (despite the fact that they rejected God's Son... their Messiah!). However, interest in Israel at government levels has always had more to do with their control of world banking.