With President Bush set to head north of the border in a state visit to Canada, a Canadian official has been advising Washington on a critical political issue. A Montreal city councilman has been in contact with District Council Chairman Linda Cropp regarding the Montreal Expos-now-Washington Nationals baseball team sending warning that D.C. should beware. The Post quotes a letter sent by Montreal’s Marvin Rotrand: MLB’s honeyed words are only calculated to open the public…