"After that, in my vision at night I looked, and there before me was a fourth beast - terrifying and frightening and very powerful. It had large iron teeth; it crushed and devoured its victims and trampled underfoot whatever was left. It was different from all the former beasts, and it had ten horns.
Daniel 7:7
The dragon stood on the shore of the sea. And I saw a beast coming out of the sea. It had ten horns and seven heads, with ten crowns on its horns, and on each head a blasphemous name... ...People worshiped the dragon because he had given authority to the beast, and they also worshiped the beast and asked, "Who is like the beast? Who can wage war against it?"
Revelation 13:1,4
The beast described in Revelation 13 and the fourth beast of Daniel 7 are extremely similar. they both have ten horns and appear invincible in battle. However, the beast of Revelation 13 has attributes of all 4 of the beasts of Daniel. Revelation 13:2 explains it resembled a leopard but had feet like those of a bear and a mouth like that of a lion, linking it to all four of Daniel's beasts.
As I have already explained, the first three beasts of Daniel are the USA, Russia and China respectively. The fourth beast of Daniel is even stronger than the first three, yet from Revelation also has attributes of all three of them. Revelation 13:7 explains that it is given authority over every tribe, people, language and nation. I therefore think only the United Nations fits this description (or perhaps some future iteration of it - the UN having already evolved from the League of Nations after World War 2). If the beast is the UN, then both Daniel and Revelation make sense: Daniel saw the US, Russia and China as separate superpowers, while John saw them as part of the UN - both are true.
The beast has ten horns. One interesting feature of the United Nations is that it is governed by the Security Council, which has five permanent members, and ten temporary members, which are taken from five regions:
I think we can consider the five permanent members as five horns, and the other five horns as being the five regions listed above. However, it is possible there will be further evolution of the UN's structure, so I am not certain if these are the ten horns, but it is plausible.
The beast, which you saw, once was, now is not, and yet will come up out of the Abyss and go to its destruction.
Revelation 17:8a
I believe this is a reference to Genesis 11:1-9; once before mankind was united under one rule, and chose to build the tower of Babel, before God intervened and scattered mankind over the face of the whole earth.