The military on Sunday also said the bodies of the two pilots have been recovered.
The AH-64D Apache Longbow went down about 5.30pm on Saturday during combat operations west of Youssifiyah, about 15km southwest of Baghdad, the US command said in a statement on Sunday.
"The soldiers' remains were recovered following aircraft recovery operations at the crash site" of the helicopter "which went down due to possible hostile fire", the statement said.
No further details were released.
It was the first loss of a US helicopter since three of them crashed in a 10-day period in January, killing a total of 18 American military personnel. At least two of those helicopters were shot down.
Elsewhere in Iraq, three other US soldiers were reported killed on Sunday
The US command said two soldiers were killed by a roadside bomb late on Saturday in central Baghdad and another died from non-hostile related injuries suffered near Kirkuk in northern Iraq on the same day.
US soldiers face daily attacks
The five US deaths brought to at least 2,333 the number of US service members killed since the Iraq war started in March 2003, according to an Associated Press count.
In Ramadi, 112km west of Baghdad, a roadside bomb exploded on Sunday near a US convoy, blowing parts of a vehicle onto the roof of a nearby building.
No US casualties were reported.
Elsewhere, six insurgents were killed on Sunday when a homemade bomb they were building exploded inside a house in Madain, about 25km southeast of Baghdad, police said.
The Iraqi joint command centre in Baquba reported that attackers blew up a small Shia mosque on Sunday in the region, some 55km northeast of Baghdad.
However, Major Tim Keefe, a US spokesman in Baghdad, disputed the report, saying American troops went to the reported location and "were unable to find any mosque that had been damaged".
Iraqi authorities at the command centre said they were not authorised to give any details on the bombing report.