Since the name has an accent over the "e", the second syllable should be stressed not the third. Without the accent however the third syllable is stressed. [noted -ed]
I agree, the name has Italian origins as well as Spanish and Portuguese. This is my Grandfather's name and his parents came from Italy to America (hence the reason he was named that? Not sure.) He goes by the nickname of 'Chipper' though; Americo is for formal purposes only.