Iran Shelling Iraq

When I read this a few days back, I was amazed that I hadn't seen anything about this in the American press. If it's true that Iran has been shelling Kurds in Northern Iraq, and that Iran and Turkey are talking about conducting operations across the Iraqi border to root out Kurdish rebels, how can this not be pertinent to the US operations there? You would think that America's current enemy #1 shelling the country in which more than 100,000 US soldiers are stationed and which is already in a low-level civil war would be setting off a lot more alarms. Not to mention, Kurdistan has pretty much been the only stable region of Iraq until now. So how is the US addressing these actions?