The homemade bomb was detonated as a military convoy passed through the city of Mosul on Sunday.
Sergeant Kelly Tyler of the 101st Airborne Division confirmed the death, adding that two other American soldiers were also injured in the blast.
Elsewhere, a 12-year-old Iraqi was killed by a bomb that had been disguised as a heap of rubbish, southeast of Baghdad, according to occupation forces.
The bomb exploded near the Iskandariya suburb on Saturday.
The child's body has been handed over to Iraqi police.
On Friday, four Iraqi civilians were also killed and a dozen wounded when resistance fighters detonated a bomb in a crowded Baghdad shopping street when a US convoy passed, also killing a soldier.
An occupation administration statement said the attack was another example of Iraqi civilians becoming "targets... in an effort by anti-coalition forces to prevent establishing a safe and free Iraq."
But when questioned about the civilian toll from that attack, one resistance fighter – calling himself Abu Muhammad – told AFP: "It's true Iraqi deaths hurt us but it is a question of priorities."