A late penalty by USA fly half Kimber Rozier proved the difference as Wales fell to a 7-10 defeat in their 2014 World Cup warm-up match at Pandy Park in Cross Keys.
Both sides scored one converted try apiece with winger Vanesha McGee ploughing over for USA and No 8 Sioned Harries replying in the second half for Wales.
Both sides ignored the wind and rain to play an open game of rugby with McGee and full back Akilaini Baravilala a constant threat with ball in hand for USA while Dyddgu Hywel and Laurie Harries featured regularly in counter attacks for Wales.
The teams were deadlocked until the 39th minute when USA ran the ball right and McGee dived over to score a well-executed try despite the best efforts of Harries and Hywel in defence. Rozier landed an excellent conversion to give the Americans a hard fought 7-0 lead at the interval.
Wales got back in to the game in the early stages of the second half through their forwards with Caryl Thomas and Catrin Edwards willing workhorses.
Wales got back on level terms in the 60th minute after holding onto possession for several phases. The ball was spread wide where Sioned Harries was lurking with intent and the speedy No 8 showed a clean pair of heels as she cut back against the grain to score under the posts. Laurie Harries added the extras to bring the scores level at 7-7.
Wales continued to attack but were guilty of coughing up possession at crucial times. USA made them pay by bursting downfield to set up Rozier for a penalty after Welsh forwards were penalised for coming in at the side of a ruck. The fly half had no trouble striking the ball between the uprights to edge her side back in front.
Wales finished the match in the ascendency but couldn't find a way through as USA held out for a gritty win.
Despite the narrow defeat, Wales Women's head coach Rhys Edwards was satisfied with his team's efforts.
"Going into the game we didn't know much about them but we knew it was going to be a tough game, especially as they are ranked in the top five teams of the world. The scoreboard doesn't really reflect that so I'm pretty pleased with the performance.
"We created some chances against one of the best teams in the world - the difference being when they get a chance they score, we don't. We take two, three, four or five times to get on the score board. We've got to show some composure and a bit of belief but we are certainly knocking on the door.
"We are improving and we showed that today. As we look ahead to the World Cup, we have another game against Ireland and there is no reason why we can't kick on from there and challenge in France."
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Bedwas head coach Steve Law and players Nicky Griffiths and Alun Rees extol the virtues of the close knit club as they prepare to host third place RGC 1404 - who are one place head of them on the Principality Premiership points table - on Saturday.
Many of the Wales squad have said Diolch (thank you) to someone who played an important part in their early playing days by nominating them to be invited to the Wales v South Africa match. One person, Gowerton Comprehensive geography teacher Mr Dean Mason was nominated by two of his former pupils, Dan Biggar and Sam Davies.
The second WRU disability rugby pilot has been delivered, this time in Caerphilly schools, culminating in a festival at the Caerphilly Centre of Sporting Excellence, Ystrad Mynach tomorrow. Plans are in place to set up a Disability Rugby Club in Newbridge to provide long-term playing opportunities.
WRU TV: Hear from inside the Wales camp as Neil Jenkins discusses this weekend's clash with South Africa and how the squad are looking to put in a strong performance to round of the 2016 Under Armour Series