UPDATE 31 December 2019 11:04 [Borepatch]: Trump's response:
Iran killed an American contractor, wounding many. We strongly responded, and always will. Now Iran is orchestrating an attack on the U.S. Embassy in Iraq. They will be held fully responsible. In addition, we expect Iraq to use its forces to protect the Embassy, and so notified!— Donald J. Trump (@realDonaldTrump) December 31, 2019
I guess we'll see if the Iraqi government has the security services stand down again.