The actual answer is when Adam and Eve were expelled from the garden.
Despite those that believe in "evolution", everything in human history since then has been a downward spiral - "devolution" if you will.
The USA is just one more in a long series of failing (devolving) empires... the ink wasn't even dry on the Constitution when the process had begun.
According to that logic, it is impossible that the USA ever existed. I think you need to do better than that kind of reasoning. The way we perceive the world and define it in the West is over 2500 years old. Things are cyclical, and your religious beliefs should remain figurative.
