Good point! If you add Southern Ontario, Toronto and Rochester areas, which is realistic, we become the 4th largest metroploitan area in North America with over 11 million in population.
"Extended Golden Horseshoe
Under the most recent defiintions, the population was 7,910,585 in the 2001 census with an estimated popluation of 8,600,000 as of 2006, of these people approximately 5,600,000 live in the Greater Toronto Area. Following the guidlines of the Metropolitan Combined Statistical Areas, it's the 5th most populated greater combined urban area in North America after New York City, Mexico City, Los Angeles, and Chicago. There is a further, but less used definition which extends across the border into western New York state, including the Buffalo-Niagara Area and Rochester, New York urban areas. The total population in this definition is almost 11 million (hence the 4th most populous urbanized region in North America)."