Tighthead prop Keagan Bale caught the eye, carrying the ball with real purpose while captain Todd James set the perfect example from No 8 with a high work rate in defence.
Winger Martyn Davies bumped off players seemingly at will en route to the try-line for his try while his fellow winger James Whittingham set Wales on their way to victory in just the second minute when he touched down.
Harri Millard then got in on the act, scoring Wales's third try which Jarrod Evans added the extras to give Wales a handy 17-3 lead at the break after USA's Sam Cowley hand slotted an earlier penalty in reply.
After the break USA jumped out of the blocks with winger Stratton Brown scoring in the first minute after the re-start. But Wales regrouped to see Bale score a well deserved try while Whittingham secured his second try of the game.
Evans added another penalty to put clear daylight between the two sides but the Americans had the last word with hard running centre Fitou Fisiiahi scoring a try.
Wales will now play France Under 16s tomorrow before completing their programme against England Under 16s on Wednesday and England South U16 on Friday.
Wales: Tries - Whittingham (2), Davies, Millard, Bale; Con - Evans; Pen - Evans, Sheedy.
USA: Tries - Fisiiahi, Brown; Pen - Cowley