The political system of the ancient roman empire was characterized by

In the rein of Augustus, the Roman Empire was governed by Dictatorship. He became the first emperor. Following his father's (Caesar) wishes of becoming first emperor. But way back, Ancient Rome was governed ana structured by a coalition of patricians. It was also governed through religion, as they believed in order to sustain a better future for the Roman world, they had to pay their respects to their Gods, their deities, so they would be blessed forever and always. They also has a podium, ranking from slaves to High Patricians, who were both rich in money and resources, which both included natural and clients. However, after Augustus's rein, Rome was governed by Emperors, with help of the Senates and consuls. The Emperor obviously getting the upper hand in discussions. 
Also, think about the Pax Romana. This too should give you an idea.

I hope I helped you. I sure do hope you understood all that gibberish. Lol

From mexican american war , us gained new mexico.