Sonny Milano tied the game midway through the third period and scored the lone goal of the shootout as the United States erased a pair of deficits to top Ontario 6-5 in Saturday's Group B opener at the 2013 under-17 world hockey challenge.
The game marked the first preliminary round meeting between the two since 2006, although they met in the 2008, 2010 and 2011 gold medal games - Ontario won gold in the first and last of those match-ups, while the U.S. earned the top prize in 2010.
Jack Eichel scored twice to lead the Americans. The U.S. hasn't lost its first game of the tournament since 1997.
Ryan Hitchcock and Keegan Iverson had the other goals for the U.S.
Connor McDavid of Newmarket scored and added two assists for Ontario in an impressive debut for the 15-year-old, while captain Aaron Ekblad of Belle River had a goal and an assist.
Josh Ho-Sang of Thornhill, Daniel De Sousa of Mississauga and Sam Bennett of Holland Landing also scored for Ontario, which had its 11-game preliminary round winning streak snapped.
After the U.S. had fought back from 4-1 down to tie the game on Eichel's power-play goal at 9:14 of the third period, it took Ontario just 22 seconds to regain the lead, as Bennett tapped in a loose puck after a rush by McDavid.
Milano brought the Americans even 2:03 later, forcing extra time.
American goaltender Chris Birdsall came up big in the shootout, stopping McDavid, Ho-Sang and Bennett, and Milano's goal on the Americans' first shot stood up as the winner.
Elsewhere in the tournament: Sweden 4, West 0; Pacific 8, Russia 7 (OT) and Quebec 5, Atlantic 2.
Sweden 4, West 0
At Drummondville, Que., Gustaf Franzen scored twice and Jesper Eriksson made 27 saves for the shutout as Sweden (1-0-0) opened Group A play with a shutout over West (0-1-0).
Pacific 8, Russia 7 (OT)
At Drummondville, Joseph Hicketts scored in overtime as Pacific (1-0-0) edged Russia (0-0-1). The Russians scored three consecutive goals in the third to force the extra period.
Quebec 5, Atlantic 2
At Victoriaville, Que., Nicolas Aube-Kubel scored twice in the second period as Quebec (1-0-0) disposed of Atlantic (0-1-0), which was led by Clark Bishop's two goals.