Shiffrin won the slalom in the resort of Gurgl by a comfortable 0.55 of a second from Italian-born Lara Colturi, who skis for Albania, in second place.
Switzerland's Camille Rast finished third down the Kirchenkar course.
"I was really nervous on the top," said double Olympic champion Shiffrin, who was last to leave the start hut for a second run that secured a record-stretching 62nd slalom win.
"I could hear all the other women going down and their teams were cheering, and that always means they had a really good run.
"I'm thinking I don't think it's happening today... push, push. It feels really satisfying to have a really great run down that slope. What a wonderful day."
Killington, Vermont, hosts a women's giant slalom and slalom on November 30th and December 1st.
Shiffrin has won six of the seven World Cup slaloms previously held there.
No skier has won 100 World Cup races and completing the landmark century in the eastern US state would be even more of a celebration for the 29-year-old, who attended ski school there.
"I guess there's a bit of pressure around it but I'll try to ignore that," she said of the 100 mark.
"If it happens it's wonderful, if it doesn't happen nothing to cry about in the grand scheme.
"But I hope to have a really good performance in front of the home crowd."
Shiffrin collected a record 87th career World Cup win in March 2023, surpassing retired Swedish great Ingemar Stenmark's mark that had stood since 1989.
