Argentina and the United States produced two more big wins to remain unbeaten going into a title showdown in the Americas Rugby Championship.

Argentina, winners of the last edition of the Six Nations-style event, romped to a 79-7 victory over Brazil in Ushuaia in Tierra del Fuego, while the United States thrashed Chile 57-9 in Santiago.

In the third match of the day, Uruguay edged Canada 17-13 in Maldonado.

Brazil started strong in their effort to make it a match against powerhouse Argentina, even taking a 7-5 lead as Moises Duque scored and converted in the wake of young scrum half Sebastian Cancelliere's opening try.

But the try would be Brazil's only one in a match that saw Argentina run in a dozen.

Two of those came from Cancelliere. Tomas de la Vega and Lautaro Bazan Velez added two apiece and there was one each from Franco Brarda, Marcelo Brandi, German Schulz, Ignacio Larrague and replacements Emiliano Boffelli and Juan Cappiello.

Boffelli, a Super Rugby standout for Jaguares last year before a knee injury ended his season, was playing for the first time since May.

His insertion was among seven squad changes by Argentina since last week's victory over Chile.

Argentina and the United States are both 4-0 heading into next week's clash for the title at Comodoro Rivadavia.

For the second time in three weeks, coach John Mitchell's Eagles scored eight tries, led by two apiece from flanker Tony Lamborn and substitute hooker Peter Malcolm.

Vice captain Todd Clever contributed one try, as did Cameron Dolan, David Tameilau and Matthew Jensen.

Having scored a combined 102 points in their prior two victories, against Brazil and Canada, the United States were keen to keep up the barrage against a Chilean team that conceded a tournament-high 98 points through their first three matches.

But ball-handling errors and a quick-to-rush Chilean defense frustrated the Eagles, and kept the halftime score a reasonably close 17-6.

The visitors, however, turned it into a rout with six tries in the second half.