5. Why did the Roman Empire fall? THAT'S THE WRONG F*K*NG QUESTION. The question you should be answering is "Why did the Roman Empire last so long?" The US is barely 200 years old; the Roman _Rebublic_ lasted 500, the empire another 500, and the Eastern Roman Empire didn't kick off until the 15th century. It's 300 years too early for you to be feeling smug toward them just because they are no longer around.
Why did they last so long? It wasn't because they had a small, weak central government with low taxes, low spending, and no support or respect from the public.