Which civilization had the greatest impact on the US government Greece Rome or Western Europe?

This question is really an opinion, but I would say that it would have to be Greece because Greece layed down the foundations for both of the other civilizations. Actually no, it didn't. Greece was a Democracy where the people ran the government and Rome was actually a Republic with representatives. Considering the U.S. government is a Democratic Republic, I would have to say Rome and Greece influenced the country's government.