The quote above is attributed to Massimo d'Azeglio, an Italian statesman, painter and writer. He was the descendent of a wealthy, and in fact noble, Piedmontese family, and lived to see most of the Italian unification, il Risorgimiento. The quote above translates to, "We have made Italy. Now we must make Italians." It's an interesting idea.
What many people in the US don't really know is that Italy (and Germany too, for that matter) are indeed ancient places with an ancient cultural legacy, but they have more than one ancient cultural legacy, and their history as a unified nation postdates the foundation of our own country. Prior to that, the map of Europe showed the Kingdom of Sardinia, the Kingdom of the Two Sicilies, Lombardy, the Papal States, Venetia, the Grand Duchies of Tuscany, Modena, and Parma, etc. When the Kingdom of Italy finally finished annexing all of the lands that it would have prior to World War I, Italy was indeed made, but many of the people therein had no identity as Italians, they had no particular loyalty to the concept of Italy, and they didn't, in many cases, even speak Italian (even today UNESCO recognizes 31 endangered languages in Italy... and they don't even publish reports on the non-endangered languages.) Starting at this period about twenty five million Italians emigrated, creating a vast diaspora that lasted for almost 100 years and is the largest population migration of modern times. These emigrant populations grew, in many cases, in their home countries; there are almost as many Italians in Brazil and Argentina alone as there are in Italy itself. The United States is another huge destination, and even Australia was an important one.
Looking back at Italy prior to the eve of Unification, you've got even more diversity. The second map shows Italy during the Crusades, and you would barely recognize the states that existed then. Oh, sure, you recognize the cities and other landmarks, but the states themselves are completely different. The Patriarchy of St. Peter, Tuscia, Romagna, the Duchy of Spoleto, Apulia, Calabria, Saracen states, Lombard states, Norman states... it's almost a completely different world.
Of course, this still postdates the fall of the Roman empire. Prior to the rise of Rome, you had other significant "empires" on what would later become Italian soil, Magna Graecia, the Etruscans, Carthaginians and more.
Why am I talking about this? I've noticed a trend in fantasy literature and in gaming, to posit kingdoms and nations that exist essentially unchanged for thousands of years. This is not only highly unrealistic, but it's just plain boring. Even in the unusual situation where a region maintains some cultural uniformity for a long period of time (like China, or Egypt, for example) there isn't political longevity to match. China in particular would have been an interesting study; as probably the longest-lived culture in the world, seeing its geographic growth and gobbling up of neighbors, seeing it's various political boundaries, the various different states that all claimed to be heralds of Chinese culture, and even the various foreign-led dynasties that eventually became so thoroughly "China-fied" that they might as well have been domestic, after a time--it would have demonstrated my point quite well.
Feel free to make the history of your campaign settings, to the extent that you delve into history at all, more dynamic. Staid, long-lived empires that maintain their borders, culture, fashion, and way of life for generation after generation after generation after generation... what's the fun in that, anyway?