Here's a list of 1 - 6:

1.
Egypt
2.
Assyria
3.
Babylon
4.
Medo
-
Persia
5.
Greece
6.
Rome

We've already concluded that the 7th kingdom is the Revived Roman kingdom - whatever form/name it takes.

I tend to refer to it as the "global world order" because many countries cooperate in terms of trade; wars through coalitions, etc; currency i.e. dollar is the reserve currency and a considerable amount of trading is done in the dollar
It has a king - unknown at this time. However, I want to address some people/entities who I think it might be.

The eighth kingdom (New World Order) - is ruled by the antichrist.