I lived in Argentina for two years before, know the culture, and speak the language. So I'd just be returning. Also, while I'm sure that there are some issues unique to and associated with being an expat living in Argentina, most people have a lot of other factors going on in their lives that are likely larger contributors to whatever they're dealing with. An expat dealing with a divorce, for example, would likely have more issues stemming from the divorce than from just being an expat. The specializing in dealing with expats would, in larger part, be about having an English speaking also expat therapist that they can see in person.