Anyone who is Muslim and living in America (particularly since 9/11) must surely be somewhat sensitive about the subject and apprehensive about how they will be seen by other Americans. I would have my journal focus on that. If I were writing as a teen, I would probably want to focus also on feelings of resentment due to the fact that I felt apprehensive.
I think I would worry about what the Christian would think. If my family is devout and we pray when that person is around, what will they think? Will the person think we're weird for not having pork? What if the person is still with us during Ramadan?
I would write a journal where I wondered about issues like this and in which I express some frustration because I don't like having to feel this way in a country where we're supposed to have freedom of religion.