My wife travels for business to different parts of the world and we have found that video chatting/FaceTime works poorly in most country's outside the US. Not sure if its the distance or just poor wi-fi in other country's. I know it shouldn't matter but it does.
Despite massive investment on world wide telecommunication infrastructure, the on-going problem is, IS NEVER ENOUGH. FaceTime (video) takes bandwidth, more than voice, and certainly more than text.
Not too long ago, making simple voice-to-voice international calls gets you echos and seconds delays, it has gotten a lot better. But of course now that we take voice comm for granted, we throw in video.
The problem is exacerbated when u go through WIFI. Do you know the WIFI bandwidth available on either end? Unless you own both WIFI you don't really know. Then VOIP (Voice Over IP or Video Over IP) hopefully goes through a QOS path. (QOS=assign voice and video traffic high priority) Currently I do not think ISPs have standardized QOS for public video transmission across international boundaries.