Interesting that the three empires you mention were all heavy slave owning powers, and very keen on conquering their neighbors to exploit economically, indeed this is why so many powers eventually achieved independence from all of those nations, both economically and politically, ---- or do you think Mahatma Gahndi was wasting his time? Not to mention hannibal and Sparticus, not to mention the marmaluk bay rebellion in egypt and likely a lot of others against the Ottoman empire (I am not as familiar with Otterman history).
it's also interesting that the three powers you site had military supremacy on their side, and a society based very heavily on competitive values and the very "rich/poor" divide you have decried in other topics.
I'm afraid the unfortunate truth is that we already! have exactly the sort of empire you are speaking of, It's not the roman empire, or the british empire, or any empire based on nationalism, it's the empire of the corporation?
don't believe me, look at the amount of political, economic and social power the super rich have, power which transends national boarders, and how those who maintain that power, e.g workers in third world countries or even in first world ones are treated.
the plane fact is humanity doesn't change at all, and will not change until we rethink our ideas about power, and how we treat people in our society.
But since that would actually require someone thinking! about things rather than everyone just grabbing selfishly after whatever economic, political or social power they can, that is not going to happen at all.
A united earth with everyone sharing equally and caring for each other Startrek style is a lovely vision, sadly humanity is, and always has been the wrong species to make it happen.
With our dreaming and singing, Ceaseless and sorrowless we! The glory about us clinging Of the glorious futures we see,
Our souls with high music ringing; O men! It must ever be
That we dwell in our dreaming and singing, A little apart from ye. (Arthur O'Shaughnessy 1873.)