Six of the Cup quarterfinal spots are still up for grabs
The Blitzbokke made a convincing start to their Las Vegas Sevens title defence by not conceding a single point on the opening day.
Seabelo Senatla returned from injury to score four tries, while Branco du Preez and Justin Geduld both scored three tries as they beat Wales 43-0 in their first match and Canada 29-0.
Mathematically the Nelson Mandela Bay South Africa Sevens champions can still miss out on the quarterfinals, but they have all but secured a place should they lose to Kenya and Canada beat Wales.
At the end of an enthralling Day One of the USA Sevens in Las Vegas, Round Four of the Sevens World Series, six of the Cup quarterfinal spots are still up for grabs going into the third round of pool matches on Day Two.
Up until the 16th and final match of the day all eight were available, but France broke the USA's hearts with a narrow 14-12 victory to book their place in the Cup quarterfinals.
Matt Hawkins' side will now compete in the Bowl after an earlier narrow 19-12 defeat at the hands of Argentina, with Los Pumas also progressing to the Cup and ending day one with a 100% record.
Current Series leaders New Zealand and Samoa also won both of their two matches but it was defending champions South Africa that impressed the most scoring no fewer than 72 unanswered points.
Kenya, having lost 17-15 to Canada in their first match, went on to beat Wales 21-17 with Biko Adema scoring 11 points and captain Collins Injera, who was in inspired form, scoring the winning try for Paul Treu's side.
In Pool B it had looked as though the Gold Coast champions New Zealand and Dubai champions Fiji were set to qualify but Cameron Clark, returning to the Australian side from injury, stepped up to kick a winning drop goal penalty with the last play of the match to beat Fiji 22-21 and throw the pool wide open.
Forwards Sam Dickson and Scott Curry both scored in New Zealand's 31-7 win against Australia, before Tim Mikkelson added a brace and a conversion in their 26-5 defeat of Scotland as the current Series leaders look to build on their two point lead at the top of the standings in Las Vegas.
England lost to Samoa 22-19 in their first match, but 16 points from captain Tom Mitchell ensured they impressively won their second match 54-0 against Portugal in Pool C and they sit on four points alongside Portugal, while Viliamu Punivalu's side have six.
The hosts, USA, were unfortunate to lose to Argentina 19-12 in their opening match, despite an impressive try from Carlin Isles, and 14-12 against France in the final match of the day with Les Bleus earlier beating Spain 47-0 thanks to 18 points from Stephen Paraz to progress from Pool D.
Spain, Wales, Scotland and Uruguay will join the USA in the Bowl. Uruguay, competing in their first World Series event of the Series as the only non core side, and having just booked their place at the core team qualifier in Hong Kong in March almost upset the apple cart even further in Las Vegas, leading Samoa, winner of this tournament in 2010 and 2012, 12-5 at half time before losing 17-12.
Day One results:
South Africa 43-0 Wales
Canada 17-15 Kenya
New Zealand 31-7 Australia
Fiji 24-0 Scotland
Samoa 22-19 England
Portugal 19-5 Uruguay
Argentina 19-12 United States
France 47-0 Spain
South Africa 29-0 Canada
Kenya 21-17 Wales
New Zealand 26-5 Scotland
Australia 22-21 Fiji
Samoa 17-12 Uruguay
England 54-0 Portugal
Argentina 33-5 Spain
France 14-12 USA
Day Two fixtures:
Wales v Canada
Australia v Scotland
England v Uruguay
Argentina v France
Samoa v Portugal
New Zealand v Fiji
South Africa v Kenya
United States v Spain