Quoting Libertarian ♥:" As a superpower, many believe that only the United States has the combination of military, economic and ... [snip!] ... like child sex slaves. And countries that are happy with their policies, and don't want Americans there to change things."
Yes, within reason. officially and unofficially, the USA is the defense for many, many countries.
For those countries to which we arent their defense, i think we sometimes have a responsibility especially if it's in our own interests (i.e. protecting our oil supply and the oil supply of key allies).
For other countries like Rwanda, I'm torn. after seeing Hotel Rwanda, I'm embarrassed that we didnt do much, much more.
It's a hard call but clearly we cant afford it right now.