Alex Morgan also scored twice and was instrumental in both of tallies by the 31-year-old Wambach, who increased her total to 131 and moved one goal past retired American Kristine Lilly in career scoring. American Mia Hamm, who retired from the international game in 2004, holds the record with 158.
"It's great to feel the gold," U.S. coach Pia Sundhage said. "Today we decided to go not with one of the best players, Lauren Cheney. She hasn't been in the starting lineup. But the combination with Abby and Alex Morgan turned out to be pretty good."
It was the 43rd victory claimed by the United States in 51 matches over Canada, which disputes one of the wins as not an official match.
Both teams clinched their places in the London Games on Friday with semifinal victories. The United States beat Costa Rica 3-0, while Canada subdued Mexico 3-1. It was the first loss in five games by Canada, while the United States was the only team to win every game -- by a combined 38-0.
Sunday's game was largely for bragging rights between the North American rivals. The result extended the Americans' unbeaten run against Canada to 25, having not lost since March 2001.
The Americans used a high-defensive line to press Canada from the start, catching the host offside twice in the first three minutes and going ahead in the fourth minute.
Carli Lloyd played a ball out of the back that Wambach flicked backward with her head from just inside the Canada half. Morgan sprinted past Shannon Woeller, who played every minute of every game in 11 days, and shouldered off Candace Chapman before finishing from the edge of the penalty area past goalkeeper Nicole Barnhart.
Canada didn't manage a shot until Chapman's header that was high and wide in the 16th minute, and Wambach doubled the United States' lead in the 24th.
Morgan raced past Woeller again down the right side of the penalty area before chipping a cross into the near post, where Wambach volleyed a sharp header past Barnhart.
Wambach scored her second of the game and sixth of the tournament four minutes later. Lloyd found time and space from 30 meters and drove a low, left-footed shot off the right post. The rebound came to Morgan, who played the ball square to Wambach, who volleyed it with her right foot.
"The first half, everything they hit, hit the back of the net," Canada coach John Herdman said. "That's the difference with the U.S. When they're hot, they're hot. They were white hot tonight. That's what they can do to teams. We've seen them destroy teams over the last few years. "
Canada struggled to hold possession in the U.S. half and get behind the American backs, but finally broke through in the 44th. However, U.S. keeper Hope Solo was quick off her line to block Christina Julien with a sliding, sprawling effort.
"When Hope comes out and makes that save, she gains confidence and we can confidence," Sundhage said.
The United States effectively nullified Canadian forward Christine Sinclair, who entered the game tied with Wambach in career scoring with 129 goals and finished as the tournament leader with nine.
The Americans were playing their fifth game in 10 days, one less than Canada, but still displayed superior speed. Morgan's pace resulted in the fourth U.S. goal.
Second-half sub Cheney launched a long ball from her own half over the top, and Morgan timed her run to stay onside of the last defender, Woeller.
Rhian Wilkinson tried to chase down Morgan, who moved inside to avoid the challenge. Morgan rounded Barnhart, but then had to pivot 360 degrees to elude Woeller, who had ran back, and then scored into an open net.
Canada will head to the Olympics for the second straight time, while the Americans will be making a fifth trip, this time as a three-time and defending champion.