Wales took the lead early on with a try from Full back Elen Evans but the USA kicked a penalty and added a try from an intercepted pass to give USA the lead 8-7 at half time.
Wales picked their game up in the second half and started to play some good rugby but a high penalty count halted several advances. Finally, winger Gemma Williams added their second try in the corner following some good work by the Welsh pack. Paula Mullen converted her second try of the match to give Wales the lead, 14-8.
In the dying minutes, Wales added their third try to bring the final score to 19-8. Second row Beth Hawke gained her first cap at Under 19 level after joining the training squad from the Welsh Under 16s last weekend.
Wales play Canada at Pill Harriers next Saturday (1pm KO)