The U.S. have never failed to reach the last four and the tournament favourites were not going to be denied by an Italian squad of rank outsiders playing in just their second Olympics.
Megan Keller scored the only goal before the first interval. Kendall Coyne then twice found the back of the net along with strikes from Laila Edwards, Britta Curl and Hannah Bilka in a five-goal second-period outburst that provided a more realistic look to the score.
Sweden made the last four with a 2-0 win over the Czech Republic earlier on Friday. Defending champions Canada face Germany and Finland take on Switzerland in the other quarter-finals on Saturday.
Teams will be re-seeded after the quarterfinals matches to determine the semifinals pairings.