The Iranian attack was in retaliation for the U.S. drone strike near Baghdad airport that killed a top Iranian commander, Gen. Qassem Soleimani, prompting angry calls to avenge his slaying.
An Associated Press crew touring the Ain al-Asad base Monday saw large craters in the ground and damaged military trailers as well as forklifts lifting rubble and loading it onto trucks from a large area the size of a football stadium.
The air base in Iraq's western Anbar province is a sprawling complex about 180 kilometers (110 miles) west of Baghdad shared with the Iraqi military and housing about 1,500 members of the U.S. military and the U.S.-led coalition fighting the Islamic State militant group.
It was struck by Iranian missiles on Wednesday in Iran's most direct assault on America since the 1979 seizing of the U.S. Embassy in Tehran. The proxy attack raised fears of a wider war in the Middle East although both sides have since then indicated there would not be further retaliation on either side, at least in the short term.
The U.S. said no American soldiers were killed or wounded in the Iranian attack.
"There were more than 10 large missiles fired and the impact hit several areas along the airfield," said Col. Myles Caggins, a spokesman for the U.S.-led coalition fighting Islamic State forces in Iraq and Syria. He added that the explosions created large craters, knocked over concrete barriers and destroyed facilities that house dozens of soldiers.
Although no soldiers were killed, he said several were treated for concussions from the blast and are being assessed by professionals. Myles added that troops received notification the missiles were on their way thanks to early warning systems, and troops were moved out of harm's way. He described soldiers who lived through the attack as "warriors."
The Ain al-Asad air base was first used by American forces after the 2003 U.S.-led invasion that toppled dictator Saddam Hussein, and later saw American troops stationed there amid the fight against the Islamic State group in Iraq and Syria.
President Donald Trump visited the sprawling air base in December 2018, making his first presidential visit to troops in the region. Vice President Mike Pence has also visited the base.