Los Angeles - Second-half tries by Santiago Medrano and Segundo Tuclet powered defending champion Argentina over Canada 20-6 Saturday while the United States edged Uruguay 29-23 in Americas Rugby Championship openers.
The Americans and Argentina joined Brazil, a 17-3 winner over Chile in Friday's first match of the Six Nations-styled tournament, atop the table.
Snow frustrated scoring for Argentina and Canada in the first half at suburban Victoria, Canadian captain Gordon McRorie and Argentina's Domingo Miotti exchanging early penalty kicks for a 3-3 half-time deadlock.
But Medrano put Argentina ahead to stay with his 50th-minute try, grabbing and touching down a grubber kick from Miotti.
"The team was very excited," Argentina captain Lautaro Bavaro said of the match played in frigid, snowy weather.
McRorie, a 28-year-old Hong Kong-born scrumhalf, hit another penalty kick in the 62nd minute.
But second-half substitute Tuclet, who made an appearance for Argentina's Super Rugby Jaguares last season, boosted the visitors' lead to 17-6 with a 67th-minute try and Miotti added another penalty kick with five minutes remaining to finish the scoring.
At San Antonio, US captain Blaine Scully scored the go-ahead try in the 61st minute and the Americans held off Uruguay.
Scully, a 28-year-old winger for the Pro 12 Cardiff Blues, collected a kick from Will Magie out of a US maul in the corner of the try zone and the hosts never trailed again.
Scully's try put the Eagles ahead 26-23 and Irish-born A.J. MacGinty added a final penalty kick in the 66th minute to give the Americans their final victory margin.
But it didn't come easily. MacGinty, a flyhalf for English Premiership side Sale Sharks, missed penalty kick attempts in the 69th and 78th minute and the Eagles had to stop a late driving maul by the South Americans to complete the triumph.
"We knew it would be tough, tight and physical, which is about what it was," Scully said. "It was pretty inaccurate from us at times, but I'm really proud of the guys for digging in and stopping the driving maul, which we really struggled with for the 80 minutes."
The Eagles play host to Brazil next Saturday while Chile visits Canada and Argentina entertains Uruguay.
Uruguay opened the scoring in the fourth minute on German Albanell's penalty kick but Ben Cima answered for the Eagles in the next minute to level at 3-3.
In the 16th minute, Uruguay's Facundo Gattas dove into the corner for a try that put the South American side up 10-3.
Cima responded with penalty kicks in the 22nd and 31st minutes and the Americans seized the lead in the 38th when MacGinty ran through a gap and offloaded to Bryce Campbell, who scored the try to put the Eagles on top 16-10.
Albanell added a late penalty kick to pull Uruguay within 16-13 at halftime and the Los Teros moved back into the lead in the 46th minute on Uruguay captain Alejandro Nieto's try. Albanell and MacGinty then exchanged penalty kicks, setting the stage for Scully's late heroics.