I think this is a completely subjective topic to write about. For instance, I have had extensive international experience, and on one hand, this seems very childish to me. But I also realize that we probably have very different backgrounds. What is challenging for me may not be challenging for you (and vice versa). My suggestion is to try to narrow in on one particular aspect of your study abroad experience that you found particularly difficult and elaborate on that. Otherwise, you may come off wrong.
Also: Where you studied abroad and how you describe it will definitely impact the strength of whatever you write. Writing about cultural adjustment when studying in the UK is laughable compared to writing about cultural adjustment when studying in Saudi Arabia. Give solid examples. Paint a picture.