Calgary once did act the opposite way, that was a few years ago.
Not the anthem but the flag—when the Braves (IIRC) faced the Toronto Blue Jays in the World Series, a Canadian flag displayed by Marines was accidentally hung upside down.Soon there were T shirts with an upside down US flag and the caption
SORRY EH!At the next game it was announced the Marines had “requested the privilege” of again displaying the maple leaf flag and they got it right.