Contributions of ancient Rome to Western civilization include a republican form of government, the spread of Christianity, and basic principles of architecture. In addition, the Latin language has had a far-reaching influence on modern languages, especially on English.
The founders of the United States in large part designed their new government on the principles espoused in ancient Greece's democracy as well as ancient Rome's republicanism. From the Roman republic came the principle of a republican government which allows citizens to elect their leadership, which is in turn responsible to those citizens.
It was through ancient Rome that Christianity spread throughout the Western world. Because the Roman empire was so vast, they created excellent road and transport networks which allowed for the quick spread of goods and ideas. Christianity was able to spread from Palestine to England. Once the Roman emperor Constantine made Christianity the official state religion of Rome, the religion was able to flourish even more, ultimately reshaping the history of the West.
Roman architecture introduced elements that continues through history and are still seen in modern architecture. Roman architecture used the arch extensively, making possible architecture that hadn't been seen before. The dome and the flying buttress were other architectural innovations that were carried forward into Western civilization.
Although English is structurally a Germanic language, it was heavily influenced by French following the Norman conquest. French is one of the Romance langugages, or modern languages that evolved from Latin, along with Portugese, Italian, Spanish and Romanian. Close to 60 percent of the words in English ultimately derive from Latin or French.