When most people think of an "American Character" they think of hero, the restless mover, the cowboy who never stops searching for something more. The appearance of the American is that they are always leaving the place they just found, because they are never satisfied with what they have. However, in a large part of America, this isn't the case. Many small town people are so satisfied that they never leave, or so used to the idea and life in their small town that they're too scared to. Either way the reality of America is that many people believe in putting down roots, raising a family and making a home their own.
To extend these ideas, many people grow up in a small town and then venture out when they are old enough to be on their own. This way you get both ideas in one, adventuring in the world and chasing the new, but when you're tired and lonely there's always a home to fall back on. The majority of Americans seem to live this way, and when they are done with their adventure and ready to go back to a place where they can stop moving and call home, they settle down again in another or maybe even the same small town. The appearance and reality of America can greatly effect those living there because it makes life seem better than it is for some, leading them to not get the help they need because nobody thinks they're struggling.
This poem by Shel Silverstein shows that most are easily fooled by the appearance of something but when they only pay attention to that which can lead them to miss the reality. In the case of this poem it led two people not to see the resemblance because they were both hiding behind the appearance that fooled most.