I don't think you can get the actual text of the message like that, but you can tell when it's been triggered; use the gdata feed for the video and specifically search for the media:restriction element, like this:
http://gdata.youtube.com/feeds/api/videos/zYNNPfuAHa4?fields=media:group/media:restriction
It will give you a list of countries where the above error message would be triggered; something like this:
<entry xmlns="http://www.w3.org/2005/Atom" xmlns:media="http://search.yahoo.com/mrss/">
<media:group>
<media:restriction type="country" relationship="deny">PR GU VI CA DE US UM AS MP PM</media:restriction>
</media:group>
</entry>