The game between the world's two women's hockey powers was played only for pride since both teams had already clinched a berth in the semifinals. Neither will play again until next Monday.
Agosta scored Canada's first goal on the power play to create a 1-1 tie 2:21 into the third period, Hayley Wickenheiser put the Canadians in front 1:33 later and Agosta then made it 3-1.
The United States got a goal back from Anne Schleper with 1:05 to go.
In the other final Group A game of the tournament, Finland defeated Switzerland 4-3 on an overtime goal by Jenni Hirkoski.
The revised format for this year's women's tournament placed the top four teams in the world in the same group with all of those teams assured of reaching at least the quarterfinals.
Switzerland will thus play a quarterfinal game even though it is winless in the tournament. The Swiss will meet the winner of Thursday's Group B game between Sweden and Russia. Finland will play the loser of the Sweden-Russia game in the other quarterfinal contest.
The two quarterfinal winners will then move on to meet Canada and the United States. Those two countries are heavily favored to play again in the gold medal game on Feb. 20.