Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Prūsĭas, ae, and Prūsĭa, ae, m., = Προυσίας, a king of Bithynia, who hospitably received Hannibal, but afterwards betrayed him to the Romans, Cic. Div. 2, 24, 52; Nep. Hann. 10, 1; Just. 32, 4, 2; Liv. 37, 25; Val. Max. 3, 7, 6 ext.
Form Prusia, Liv. 29, 12, 14.
Hence,