The woman, who was driving back from a night out, reportedly lost control of her car after a roundabout and hit Giovanni Zanier at around two thirty in the morning.
Her blood alcohol level was reportedly four times the legal limit.
Zanier's mother had told him to walk back from the bar he had visited with two friends, even though his home was several kilometres away.
The two friends were not injured in the crash.
The US woman, who has not been named, works at the nearby AVIANO USAF base, one of the biggest in Europe. She has been placed under house arrest, charged with vehicular homicide. The results of the blood alcohol and drug tests will be made public shortly, police said.
The soldier sustained minor injuries due to glass fragments and her air bag. The local council at Porcia recently ordered street lights in the area to be turned off at 2:00am, but police said the accident would probably not have been averted, even with the lights on.
