The Greek civilization and the Roman Empire both started out on the same principles, as city states. The unusual shape of its coast and mountains that ran through its territory separated the cities of Greece. On the other hand Rome was in the middle of the Italian Peninsula. On the East a mountainous region, on the west the Mediterranean Sea, for this reason Rome was susceptible to invasions and migrations from the north and from the south.
The two major influence of cultural and ethnic is clearly visible, first by that of the Etruscans coming from the north, and the second were the Greek colonist in the south. Over time the Roman city-state has emerged as a unique city, from its Etruscan beginnings and influence, Rome was prepared to spread its own teachings. The Greek civilization has spread its influence over the Mediterranean , however, the harsh separation of the Greek city-states, meant that the colonizing the Mediterranean would have to be done by city states them self, and not as a united nation. The Greek cities did not permit the building of an Empire and the strict rules to the prolongation of citizenship stopped any specific city state from becoming to powerful. No example more obvious than when the Athenians were on their way to become a powerful Empire by their control over the Delian League, but the Peloponnesian Wars put an end to it.
The Roman and Hellenic Gods are similar because they are the same, just with a different name. But the Roman Gods rarely acted like their Pollyannaish cousins who had joined their Greek worshipers thru their life. The Gods of the Romans were State representatives. Each God looked after his own section with great sense of justice and deep prudence, but in return he was clear about the essential obedience of his followers. This respectfulness the Romans delivered with meticulous care. They never demonstrate a personal relationship or a friendship which had flourished between the Greeks. Romans didn't copy the Greeks government, but originating from the same Indo European area as the inhabitants of Greece, the history of the Roman Empire is quite similar to the Hellenic cities especially to Athena. They didn't find it hard to relive their tribal chief or their king, of their power. But once the rulers had been kicked out from the city, the Romans felt the need to fight the great power of the patricians, and it took the Romans centuries to let the free man of Rome affiliate them self with the political part of Rome.
After the city of Rome was formed into a republic government they enjoyed one advantage over their Hellenistic cousins. They conducted their political issues and other business of their Empire without too many public speeches. They were not as inventive as the Greeks and not as well-spoken and they liked the idea of actions speak louder than words. They knew the people of Rome too well to spend precious time upon talk. This is where the comparison in International relations comes. Alexander the great never did what he said; Julius Caesar never said what he did. Because of this the Romans placed the job of governing Rome into the power of two councils who were similar to a president in present day. The councils had to go thru the Senate, if they wanted to make new laws, or change the old ones. Because of tradition and clear advantage to the patricians, they elected the representatives of the Senate from their own circles. But their power had been very restricted because of the up rise of the plebeians. And later the plebeians became part of the Senate to.