Adam Siddall added two penalty goals for the U.S. (1-1)
Gordon McRorie put Canada (1-1) on the board in the 52nd minute on a penalty.
Stanfield scored his second try on a handling error from Canada to give the U.S. a 13-3 edge in the 65th minute. His first try opened the scoring 10 minutes into the match.
Earlier, Argentina remained undefeated at the four-team tournament by beating a winless Uruguay squad 31-9.
Canada plays Argentina on Sunday while the U.S. takes on Uruguay.