Societies and cultures has only grown disproportionally larger and clunkier, and the rapid expansion of societies and empires have had to adapt, change, and think about different things; however, The relevance of the beginnings of political philosophy though not as obvious or prominent still exists. After Aristotle died the Roman empire conquered many countires and nation states. The expansion could not keep the same methods, in fact, there was rapid and large scale changes. The move from city state to empire was a large one and much was involved in the expansion; nevertheless some of plato's ideas still rang true and even some of it can be sene in our own day and age here in the United States.
In ancient Greece politics was centered around city states and other smaller bodies of governance and plato gave very little thought as to dealing with conflicts, because he had focused on his own version of government; on the contrary, when the Roman empire was in power, much of it was more practical so that many aspects were different, and in this way much of plato's ideas was not practical. In Plato's time he was very surrounded just by one citt. From the perspective from a modern nation of decent size or even the Roman empire, it was an incredibly local type of community. This freed the elites and government officials to think and to have time for philosophy. There was simply no time to have this leisure of thinking and espousing of philosophy. Every move was quick, and more practical things were necessary. The citizens needed ruling. The different interests and identities needed rectifying or catering to. Foreign countries was a struggle. One could be diplomatic. At other times, they were thinking about conquest. One also had to keep in mind that they had to attempt to keep the conflict in the government out. The system of federalism takes time, people, and their minds. There was no time left to think so a lot of what expansion did was to have dampen and killed much of political philosophy. They kept conquering many countries and because of this the roman empire was rather diverse. Furthermore, the land that they acquired became larger. Their geographical area drastically expanded. The roman empire was always expanding and rapidly as well. Because there was more citizens or people in general there was a need for more and a larger number of the ruling class. Also for this reason, the local city states type of government didn't work and largely became local powers and was under a federal system. However much this is, one should be careful to not declare that Plato had no influences and absolutely became irrelevant.
Although very many of his ideas are impractical, lofty, and made for a past time, which was governed by city states, there are some ideas which are very relevant to large nations and empires. Plato's idea that everything is natural doesn't work, not especially if you're trying to rule a large amount of space like an empire. The roman empire was nothing like natural things. Another idea which doesn't work is Plato's idea of a philosopher king, who had nothing in common with his citizens. When one is trying to interact and make concessions, work with, or control diverse people this doesn't work. One almost has to get the citizen's and people involved and to love their idea of ruling them. These are examples of many of his more lofty, unworkable ideas; however, there are some sound and great theories which are espoused by plato. The entire political practice was fathered and founded by Plato. Before there was not such a practice of thinking or forming a philosophy concerning these things. Plato was generally known besides Socrates which had no written legacy of founding the practice and concept of philosophy altogether. This idea and process is still common and it has become a major field in society. The idea of the Political is also one which continues and the idea that people can not live in nature without a ruler or some form of governance. We see this echoed throught the ages of generally how one needs some form of government besides anarchy. No it may not be a Philosopher King, but something to help society along. Also, the concept of the "Good Life" has rang true. In a sense we have persisted in believing these ideas and holding various models and concepts of versions of the "Good life". The good life is Eudamonia for Aristotle and there are many forms of it afterwards throughout the roman empire and beyond. The Roman Empire was Long ago and far away and Ancient Greece may be further and more removed in time, but we can see a few of plato's thoughts still enduring.
Plato still rings true not just for empires in general but in a sense more immediately to us, as people who live in the United States in the twenty-first century. The concept of a good life is ever present here in the United States. for someone modern such as Abraham Maslow it is self-actualization. We see it in his pyramid, where needs are down below and after you have fulfilled that level you are in the want category. At the type, is pure self-actualation. You have everything, you have your needs and wants fulfilled. You are a complete person. Another slightly older form of this is the American dream. Many in this countries, especially immigrants and conservatives goes wild for this idea. The "Good life" is to be self-sufficient. It may not be plato's idea but the idea of a higher "Good Life" and self-fullfillment is important to note. The ideas of government and how the political works and how much as a community works is still in existence. The argument between Aristotle and Plato is still presently. How much should the government step in to help and how much we should help each other in a sense is a modern example. Some believe in more governmental help and others believe one should contribute more to the community to give back emotionally. A final thing that is very lasting is the practice of the theory of Politics. It certainly hasn't gotten to be extinct yet, not yet at least. We still think and make philosophy about politics, and the concept of political philosophy is still alive and healthy. There is plenty of thinking and thought in government besides just practicality and the little more trivial mondane aspects of ruling. From Plato down, Political philosophy may have not always been flourishing and in a perfect state, but there are aspect of Plato's philosophy which can reach us.
The expansion of the romen empire, a continual trend of larger countries and empires, and the demise of the city state have made some of plato's philosophy irrelevant. This is true, but all isn't lost of his legacy and it is not just some distant practice which none can relate to. We have seen his theories pass down and revive and keep being relevant throughout the ages. The encouraging bit is, that it is still relevant today and we can even see it in our very own American society. although this discussion of theory may appear trivial and far removed from reality, It's range of issues it spans and the depth at which it impacts them in our lives and our political culture is suttle but always present; So that, if one wishes to look out for them one may be able to observe it.