Its part of the propaganda. They call dead Americans “Nato troops”. Because to the jackasses we have for generals leading our military, they are first part of a command known as “NATO”, and only Americans as a distant second.
When these announcements are made, the troops are described as "NATO troops" because the announcement comes from NATO command, not the Pentagon. It may seem like a subtle point, but that's exactly why everything is presented this way when these announcements come out of Afghanistan.
To reinforce this point, I don't think troops in Iraq were ever described as "NATO troops" whenever reports like this came out.