In other words, why is the bald eagle so often considered the symbol of American liberty? When and how did it become a common symbol? And why an eagle, as opposed to a buffalo, or a deer or something?
Wait for more experienced people, of course, but the eagle was an important symbol in Rome, as well - and so much about america ("republican" government, a "senate", the architecture of the Capitol and other governmental buildings) is rooted in an appreciation and admiration for Rome. A bald eagle, very american - and damn majestic, I can attest as an Alaskan - is a similar appropriation of Roman-ness to the fledgling nation.