Well, fist, US media does not seem to agree that "most IED attacks in Iraq were not terrorism because they were aimed at US troops".

Then, what's the difference? The fact that some people in an office at another country decided that a building has military relevance, instead of PR relevance?

Ok, some targets are clearly military. But lots of them aren't. And there's a huge amount of overlap between those "military, because we said so" targets and what most groups labeled as "terrorists" target.