"America is Great Because America Is Good"

French writer Alexis de Tocqueville  visited America in 1831.  He was fascinated by it.  He was intrigued by it.  He could not understand why there was so much order and so much respect for the law.  He wrote much about the greatness of America, but the following paragraph condenses his attitude toward America.

 "I sought for the greatness of the United States in her commodious harbors, her ample rivers, her fertile fields, and boundless forests--and it was not there. I sought for it in her rich mines, her vast world commerce, her public school system, and in her institutions of higher learning--and it was not there. I looked for it in her democratic Congress and her matchless Constitution--and it was not there. Not until I went into the churches of America and heard her pulpits flame with righteousness did I understand the secret of her genius and power. America is great because America is good, and if America ever ceases to be good, America will cease to be great!"

I just have two questions:  Who is the greatest teacher of  "good"?  If America is great because it is good, does it not stand to reason that somehow, America had to be taught how to be "good."?