The rising Munster stars scored a 24-10 win, bagging all of their points in the opening 40 minutes to put the result beyond doubt by half time.
They got off to a fantastic start with scores coming fast and early and they recorded three early tries through impressive centres Niamh Briggs and Sandra Williams, and Clonakilty number eight Jane Lowney, with 1the 7-year-old fly half Nicole Fitzgerald adding two points. After that there was no stopping the host team, as Briggs, who hugely impressed throughout the game, added her second try after a fine solo run. It was too much to come back from for the visiting Americans.
The Americans did present a better threat in the second half, with number 10 Amber Benlion especially sound with her boot, and the touring side's effective maul also presented problems for Munster who made a raft of substitutes.
They were rewarded when Benlion skipped through a number of tackles to touch down early in the second half and it was a solid maul that brought their second score before the end when Sarah Carter touched down.
Penn State will face the Munster senior team on Thursday night at Temple Hill, the grounds of Cork Constitution RFC (kick-off 7.00pm).
MUNSTER U-21 WOMEN: L Brick; A Deasy, S Williams, N Briggs, F O'Sullivan; N Fitzgerald, C Rigney; J Ryan, C Kirwan, N Cuddihy, L Healy, L Landers, K Sheehan, O O'Keeffe, J Lowney.