Fiji maintains its third spot in the overall HSBC World Rugby 7s Series and is only seven points away from New Zealand which is in second spot.
His impressive play helped lead the U.S. into the cup final in Las Vegas, defeating Fiji 19-7 in the semifinal as he crossed the chalk twice.
Argentina, appearing in their 14th Sevens final had won twice on United States soil before, but were unable to resist the power and pace of the U.S. team, who went unbeaten through the weekend.
The Springbok Sevens side finished fourth after losing 26-22 to Fiji in the bronze final.
Fiji meet USA while South Africa are up against Argentina in the Cup semi-finals.
That moved SA to 92 on the standings and extended their lead to 10 points over New Zealand‚ who could only end fifth in Las Vegas.
"The last three tournaments and the last three times we have played them we have had a solid win in Sydney, right down to the wire in Hamilton and then again today, it was right down to the wire", Friend said.
"We don't always test measure ourselves on the results‚ but also the way we play".
Then the one against Argentina, we were not clinical enough, not enough attention to detail and we got one or two technical areas wrong that cost us the game. "We have to take in the positives because we have some very tight games and fix a little bit of the mistakes that we have had and I believe we will be good to go in Vancouver", Ambaka said.
Australia lost to South Africa 29-19, hosts United States of America downed England 17-12 while Fiji silenced New Zealand 14-10 in the other main Cup quarterfinal matches.