Even more important than that piece of paper, IMHO, it's the American People. Despite all the disparaging comments routinely piled on "Americans" nowadays, IMHO, the American People still remain the most generous, magnanimous, empathic, fair-minded and independent people in the world (barring very few others, as I have not done an exhaustive survey on this) . . . largely because we have not lived under horrendous tyranny like most other major population groups of the world have. That, even more than the abundant natural resources that we have, is the fundamental strength of America.
Fundamentally, at a core level, it comes down to the other document also written by the Founding Fathers -- the Declaration of Independence: rights as human beings are endowed by our Creator, not by the government. Americans understand that better than people in most other countries.