I must add that Toronto is surrounded by other Census Metropolitan Areas (CMAs )which by statscan rules it cannot merge with so there is no like for like comparison with Toronto's CMA's to American metropolitan areas.
so here are some other measures of size of Toronto including some of the bordering CMA's
Toronto-Hamilton-Oshawa
Toronto CMA: 7,106,379
Hamilton CMA: 860,266
Oshawa CMA: 482,359
Total: 8,449,004
Extended Golden Horseshoe:
Tor+Ham+Osh: 8,449,004
Brantford CMA: 173,530
Saint Catharines/Niagara CMA: 492,480
Peterborough CMA: 148,027
Barrie CMA: 245,586
Guelph CMA: 183,224
Kitchener-Waterloo CMA: 696,417
Total: 10,388,268