Wales were unable to break the shackles against Samoa, losing 26-0 at George.
Wales have replicated last week's performance in the second round of the IRB Sevens Series by recording one victory from their three pool games in George, South Africa.
Paul John's men faced the unenviable task of facing last weekend's finalists Samoa and eventual tournament winners in Dubai, New Zealand, in Pool C and came up short on both occasions. A narrow victory against the fast improving USA provided Wales with some consolation on a tough day's rugby at Outeniqua Park.
Chris Morgan stormed over for Wales's first try in the fourth minutea gainst USA to give Paul John's side a 5-0 lead.
The dogged Americans then hit back through Mile Pulu and with Nese Malifa adding the conversion USA had hit the front with a slender 7-5 lead.
Justin Tiperic was then sent to the sin-bin to reduce Wales to six men late in the first half.
Jevon Groves raced over to regain the lead for Wales before it was USA's turn to lose a man when Malifa received a yellow card.
Pulu scored his second try of the match before Ifan Evans restored the lead with a five pointer as Wales edged ahead 15-12.
The Samoans, already buzzing after beating New Zealand in their opening game, dominated from the outset to claim a comfortable 26-0 victory.
Captain Lolo Lui and Reupena Levasa were the heros for Samoa. Lui bagged a try and knocked over three conversions while Levasa raced over for a brace of tries. Samoa led 12-0 at the break and rubber stamped their authority in the second half with tries by Afa Aiono and Levasa.
Wales then had to overcome New Zealand to reach the main draw on day two but despite being in the hunt at halftime, the Kiwis stormed away in the second half to win 17-10.
Zac Lawrence and Ashley Beck traded tries in a keenly contested first half but the Kiwis clinical finishing proved crucial in the second spell.
Sherwin Stowers scored twice to put the pool favourites ahead before Wales finished strongly through Alex Cuthbert.
Wales squad: Lee Rees, Chris Morgan, Gareth Davies, Nicky Thomas, Lloyd Williams, Ashley Beck, Ifan Evans, Craig Hill, Alex Cuthbert, Justin Tiperic, Chris Davies, Jevon Groves
Nearly 40 players were involved in the first Wales Under 18 training session of the season. WRU National Performance Manager Gethin Watts is excited at the potential shown by the group and expects the Regional Under 18 Championship to hone their skills even further.