Greetings and salutations.
In my neighborhood there is a restaurant, "Cesar's Mexican and Greek Restaurant." I have sometimes puzzled as to what the connection between those two cuisines might be. Sorta mediterranean? Mexico colonized by latin-speakers? Use of sheep?
So, as a silly challenge, with a POD after the 476 sack of Rome (so no all-conquering Roman Empires!) - later is better - create a state or Empire that in 2009 rules Greece and Mexico and is headed (can be a real ruler or a nominal one, as in Queen of England) by someone with the title of "Caesar."
(Try to minimize the territory ruled between Greece and Mexico, although if you just make Mexico a Greek colony you have to explain how Greece projects power across the Med and through the Straits to hold Mexico in possible opposition to a variety of European predators).
Bruce