Da 2:37 You, O king, are the king of kings. The God of heaven has given you dominion and power and might and glory;
Rev 19:16 On his robe and on his thigh he has this name written: KING OF KINGS AND LORD OF LORDS.
I love Daniel chapter 2. The vision of the statue and the rock not cut by human hands that fills the earth is a wonderful image of the Kingdom of God.
Our God is the King of Kings. This phrase is used so often in Christian circles, and trips of the tongue so readily that we have lost the significance of what it really means. It does not merely mean he is the best King amongst Kings, but that he is the ultimate King over all other Kings. The rulers of the Nations are not the final authority, there is one who rules over them, just as they rule over others.
All authority comes from God. He is the source of all rule and governmental power on the earth. The message of Daniel 2 also shows that all authority is destined to return to him too. The rulers of the nations are just stewards and custodians of the authority they hold. It was not theirs to begin with, and it is not theirs to keep. God raises up who he wants, and God can just as easily take their power away. Ultimately all authority will revert to where it really belongs - The Kingdom of God. It was never God's intention that his earth should be ruled by a multiplicity of secular nations, but by one people in his image who rule on his behalf. God has not changed his mind, his Kingdom plan is still on track. The nations are just there as guardians over the earth until the rightful owner is ready to take possession.
It is interesting that this vision was given to King Nebuchadnezzar, one who's royal title was "King of Kings". He got given a dream by the true owner of that title!