The point of the discussion is to help both you and the visiting students develop cross-cultural communication skills. Secondarily, as they are strangers, or guests, in your country, your teacher is probably hoping that getting you talking to each other will lead to social interactions outside class, something that will enhance the cross-cultural communication skills of both host and visitor students.
One question worth asking is what they find most alien or unusual about your culture, and what they are having most difficulty adapting to. This will give you a sense of the main areas of cultural difference.
Another question you could ask is whether they have listened to any of the popular singers of your culture, and what they think of them. It would be interesting to compare the degree to which you know American popular music with the amount of music from your culture they know. What do your relative understandings of each others' popular music say about world culture?
Also, perhaps ask them for views about global climate change and how it should be addressed, and whether their travels have caused them to think differently about it. It could lead to interesting discussions about different national perspectives.
This question speaks loudly to me having had several foreign students live with me and go to school here. I agree about the purpose, and cross-cultural communication is truly important. Asking about the alien parts of our culture or the culture shock is also important. However, I would ask about their views of our government and does it affect their countries. Then I would ask them about their views of the US--what do they find positive, what is negative to them, attitudes about race and intermarriage, attitudes about the focus of youth toward drinking, drugs, school and good grades, --anything which affects them. I found that there was a contrast in treatment the darker the skin of my exchange student. Traveling also changes perspectives of people, and that topic is terrific. I would lastly ask about people in this country and their reluctance to speak or learn more than one language. What do these students think about this and how do they feel about it as the rest of the world seems to feel that at least two languages is important.