The American Dream is one of those loose phrases that we use in too many contexts, I think.  But by in large, Americans have had similar aspirations: aspirations to be free, aspirations not to be meddled with, not to be told what to do, aspirations that mean the whole future is ahead of you.  You can do all sorts of different things and you don’t necessarily have to do what you were slated to do in the 9th grade or the 12th grade or the first year of college.  The world is really open to you and there are so many choices that you can make and in many cases you will do as well in one choice as another.  You are not sort of fixed from the beginning:  I’m going to be a scientist.  I’m going to be a historian.  I’m going to be a farmer.  You probably could be good in all three of those roles, but you have to choose between them.