Down 23-11 with 20 minutes to play, Canada rallied behind tries from Paul Cuilini and Theo Sauder just three minutes apart to set up du Toit's kick.
With Canada down by two points and time winding down, a long run by substitute Philip Berna put Canada into American territory. The Canadians pushed their way down the pitch until they were awarded a penalty. Du Toit’s kick gave Canada the winning point and its first lead of the game.
Along with Cuilini and Sauder, Andrew Coe also had a try for Canada. Du Toit finished with nine points on three penalties.
The final leg of the two-game total-points series goes Friday in Langford, B.C. The series winner will be the North American representative for the Junior World Rugby Trophy 2015 in Portugal in May.
The North American winner will join Fiji, Georgia, Hong Kong, Namibia, Portugal, Tonga and Uruguay at the World Rugby Trophy, a second-tier competition. England will defend its title at the elite World Under 20 Championship in Italy in June.
Canada finished seventh at last year's Junior World Rugby Trophy while the Americans were third.
Canadian coach Jeff Williams opted for 12 of the 15 starters who played in an exhibition win over Romania earlier this month.
Toronto flanker Lucas Rumball captained the team.
Brendan Blaikie, Queen’s University, Markham, Ont.; John Shaw, Bytown Blues, Ottawa; Matt Tierney, James Bay AA, Oakville, Ont.; Paul Cuilini, Aurora Barbarians, Vaughan, Ont.; Adrian Wadden, Oakville Crusaders, Mississauga, Ont.; Lucas Rumball (capt.), James Bay AA, Toronto; Ollie Nott, UVIC Vikes, Qualicum, B.C.; Luke Bradley, UVIC Vikes, Port Alberni, B.C.; Dan Joyce, Trinity University, Dublin, Ireland; Dylan Horgan, UCC Rugby Club, Cork, Ireland; Karsten Leitner, UBC Thunderbirds, Vancouver; Guiseppe du Toit, UVIC Vikes, Maple Ridge, B.C.; Mitch Santilli, James Bay AA, Brantford, Ont.; Theo Sauder, UBC Thunderbirds, Vancouver; Andrew Coe, UBC Thunderbirds, Markham, Ont.
Paddy Finlay, Trinity University, Dublin, Ireland; Conor Young, Southern Districts RC, Sydney, Australia; Cali Martinez, UBC Thunderbirds), Vancouver; Reegan O'Gorman, Vancouver Rowing Club, Vancouver; Mitch Rothman, Vancouver Rowing Club, Vancouver; Tony Pomroy, Baymen, Conception Bay South, N.L.; Philip Berna, UBC Thunderbirds, Vancouver.
James Gannon, Lucas Joseph, Valdemar Lee-lo, Oliver Drew, Christian Wiessing (capt.), Braeden Hood, Jacobus Germishuys, Maciu Koroi, Louis Mulholland, Ben Cima, Seth Halliman, Fitou Fisiiahi, Ian Kinsly, Connor McRae, Scott Dean.
Gabe Romero, Nick Kwasniewski, Victor Comptat, Brian Nault, Erik Thompson, Oisin Brady, Babapelumu Adejuyigbe.