There are no specific answers to this question.  What you need to do is to think about which of these “characters” would be in favor of American expansion and which would have been opposed to it.  If I were answering this question, I would try to have two characters on each side of the question.

I would have the Native Americans as a group be one of the characters.  Clearly, these people would not think that the American expansion was justified.  I would have them saying something about how their land is being unjustly taken away from them.  The second character against expansion could be the herd of buffalo.  They could be talking about how expansion was bad because it was going to lead to environmental degradation.

One of my pro-expansion groups would be the farmers.  I would have them talk about how expansion is going to give them more of a chance to be independent.  It will allow them to have cheap land and to be able to be their own bosses.  My second would be the angel.  She would be talking about how American expansion was going to spread technology and education (after all, she’s carrying a school book) across the continent.

With these hints in mind, write a couple of sentences for each of these characters in your own words.  Of course, we do not know what your key content terms are, so you will need to remember to look for those and put them in if you have the chance.