The tension through the first half disappeared in the second in a 12-minute span when Uruguay scored three converted tries by wing Gaston Mieres, hooker Facundo Gattas and another Freitas set-up for Silva to complete Uruguay's first World Cup qualifying win over the US in 19 years.
The US will face Chile next year for the right to go to the World Cup as the Americas 2 qualifier in Pool D, with Chile's historic victory over Canada meaning the Canadians will miss the tournament for the first time.
History was made when Chile defeated Canada for the first time 33-24 in Valparaiso, after blowing a win a week ago in Langford. There, Chile conceded a penalty with 30 seconds to go and Canada escaped as a 22-21 winner.
Santiago Videla scored a try and kicked 18 points for Chile to progress 54-46 on aggregate, with an eye on their first World Cup appearance.
Chile had a 13-point lead by halftime after a superb try from flyhalf Rodrigo Fernandez, who caught Ross Braude's box kick and motored through the defense.
After halftime, Chile hooker Augusto Bhome was sin-binned and opposite Eric Howard scored to close the gap to six, but 14-man Chile also scored a try to prop Matias Dittus from a tap and go.
Videla continued to punish Canada's indiscipline, and though the visitors were nine behind with 13 minutes to go, another mistake at a restart gave Chile an easy foothold in the 22 and led to Videla's own converted try for a 33-17 lead.
While another Chile player was sin-binned for the last six minutes, Canada could cross only once.
"Fair play to South American rugby. They've really invested and they're going in the right direction," Canada coach Kingsley Jones said.
"We're getting caught up. I've made that point before and I don't think anyone can deny that when you watch the way Chile played. The competition for World Cup spots has become very competitive and we've missed out."
- With AP
