>>10969973A) It was technically an empire when it was a republic, and it declared many of it's leaders as "Imperators".
B) It became extremely unstable due to the increasing wealth gap and political parties operated by ambitious men who only cared about their personal reputation.
C) It never really stopped being militaristic in nature until the Teutoberg disaster followed by Constantine's conversion to Christianity.
A republic sounds nice and everything but not if it's unstable, there are civil wars and people being beheaded and executed simply because they had money or were prominent in the opposing political party. Plenty of similarities with America, minus the military requirements for political office and the combination of religion and state.
