irbsevens.com and James Mortimer 10.Feb.2013
Having to win by 14 or more points, USA came from 7-0 behind thanks to two tries from Carlin Isles and a decisive conversion from Nick Edwards with the last kick of the match to the delight of the home crowd.
Defending champions Samoa will face Scotland in the Cup quarter finals after winning all three of their pool matches at the USA Sevens.
New Zealand and South Africa also won all three of their matches and will meet Canada and Wales respectively.
Pool A (ENG, SCO, FIJ, POR)
Fiji, who will be without both their suspended captain Setefano Cakau and Manueli Lagai for the remainder of the tournament, won all three of their matches at the USA Sevens at the Sam Boyd Stadium, narrowly holding on to a 14-12 victory against Scotland, with Russell Weir narrowly missing a last-minute penalty drop goal and beating Portugal 21-14.
England, last week's champions, lost all three of their matches for the first time since the 2008 Adelaide Sevens, against Fiji 26-17 with two tries from Samisoni Viriviri, Portugal 21-5 and Scotland 14-0. It was only Scotland's third victory against England in 26 encounters.
Scotland beat Portugal in their first match, with Mark Robertson and Michael Fedo scoring the tries and Colin Gregor's touchline conversion proving decisive.
Pool B (KEN, RSA, CAN, URU)
South Africa became the second side to complete a 100% record, adding a 17-5 victory against Canada to an impressive 45-0 victory against the only non-core side competing in Las Vegas, Uruguay. On day two they also defeated African neighbours Kenya 15-5.
Canada defeated Kenya, which meant both of the Hertz Sevens finalists lost their opening matches with Sean Duke crossing for his 22nd try of the Series and Nanyak Dala and Jeffery Hassler scoring Canada's other tries. Hassler added two more in their 36-0 win against Uruguay.
Mike Friday's Kenyans bounced back from their opening defeat, riding their luck to come from 7-5 down and inflict a second defeat on Uruguay, Biko Adema benefiting from smart work by Oscar Ayodi.
Pool C (NZL, ARG, FRA, WAL)
New Zealand also won all of their pool matches, adding a 17-5 win against Argentina to their two wins on day one. Belgium Tuatagaloa helped the reigning Series champions beat France 21-0 with two of their three tries before they beat Wales 40-5 with Ben Lam crossing for a hat-trick.
Reigning Rugby World Cup Sevens champions Wales beat Argentina in a rematch of that 2009 final in Dubai 17-7 in their first match of the USA Sevens, before Rhys Jones scored a penalty drop goal to give them a 17-14 win against France to book their place in the Cup quarters.
Javier Rojas secured a 14-12 victory for Argentina against France, Los Pumas' first win of the day, and Les Bleus' second defeat. Both sides can still reach the Cup quarters.
Pool D (SAM, AUS, ESP, USA)
Defending champions Samoa maintained a 100% record, beating hosts USA, Spain and Australia. They came from 12-0 behind to beat Spain 19-12, with captain Afa Aiono scoring the winning try under the posts to the delight of the crowd at the Sam Boyd Stadium, before Levi Asifa'amatala and Reupena Levasa scored the tries against USA. Patrick Faapale scored 16 points in their 28-7 win against Australia.
Spain bounced back to defeat Australia 24-14 to bring an end to an impressive run from Michael O'Connor's side, who had won nine of their previous 10 matches. The hosts USA lost their opening match to Australia 26-7, although they reached the quarters thanks to Nick Edwards decisive conversion.