Is there such thing as the average American citizen?

No, and there shouldn't be.

Explanation:

It can actually offend people's feeling if you say you are AVERAGE citizen or you are BELOW-LEVEL citizen.

You know.

Hope I helped!

For the fall of Rome, it was the Huns invading from the east that caused the domino effect, they invaded (pushed into) the Goths, who then invaded (pushed into) the Roman Empire. The fall of the Western Roman Empire is a great lesson in cause and effect. A cause leads to an effect.
Hope this will help you!!