The 20-year-old, from Florida, fell from the third floor window on Via Oberdan overnight on Tuesday, Il Messaggero reported.
She was in the city, which is home to the prestigious University for Foreigners, along with a group of others from Florida, for the Umbria Jazz Festival.
One theory is that the girl, who is said to have been drinking last night, fell after leaning out of the window and losing her balance.
In May, a 19-year-old Italian fell to his death from a hotel balcony during a trip to Milan's Expo trade fair.
Domenico Maurantonio, from Padua, died after falling from the fifth floor of the Da Vinci hotel.