The US Embassy in Baghdad has urged American citizens to "depart Iraq immediately" following the strike.
"US citizens should depart via airline while possible, and failing that, to other countries via land," the embassy said in a statement.
The US strike hit outside Baghdad airport early Friday but security sources told AFP it was still open to flights.
Iran's supreme leader Ayatollah Ali Khamenei vowed "severe revenge" after the United States killed the commander of the Islamic republic's Quds Force, General Qasem Soleimani, in Baghdad on Friday.
"Martyrdom was the reward for his ceaseless efforts in all these years," Khamenei said on his Farsi-language Twitter account in reference to Soleimani, also declaring three days of mourning.
"With him gone, God willing, his work and his path will not be stopped, but severe revenge awaits the criminals who bloodied their foul hands with his blood and other martyrs' in last night's incident".