The problem this legacy poses for us is that we are always torn between our high ideals and pragmatic realism. The nation began with the tension between our ideals of universal freedom and equality and the reality of slavery. It continued with the tension between those ideals and the pragmatic conflicts between immigrant settlers and native Americans. More recently during the cold war this tension was evident in our uneasy support of unsavory dictators for the pragmatic reason that they helped, we hoped, to contain the spread of Communism.
There is no simple answer to this dilemma. I would hope we would never lose our high ideals; they are worth preserving and spreading to other nations and cultures when and as we can. On the other hand, naïve idealism can blind us to the realities of the world, and can be the cause of great damage to others.
The American burden is to learn to manage this tension between our ideals and what is actually possible in the world. “Spreading democracy” is a great ideal, but a very poor basis on which to build an effective foreign policy. If the world can avoid destroying itself in war over the next few hundred years, ideals like democracy and individual freedom may eventually, slowly, spread to other nations and cultures, but it will be a slow process, taking generations. We ought not to be so naïve as to think we can force it into any culture or on any nation in a few years. This is where pragmatism is neccessary.