Chicago, New York, and Toronto do not share identical cultural and architectural histories, so their contemporary buildings are bound to be different stylistically, having evolved in unique ways. Toronto is a significant enough cultural centre and marketplace for ideas to have its own healthily independent style in all aspects of the arts: buildings, music, theatre, design, visual art, fashion, you name it. How could it be otherwise?
No doubt it would be considered a heresy by the architects involved, but I'd venture to suggest that, to all intents and purposes, the works of the leading Toronto architectural firms are practically interchangeable: 18 Yorkville, the Hudson, One Bedford, is there really that much difference between them? I think wylie's description of what is going on as a "school" is dead on. An identical creative hegemony - resulting in buildings identical to our dominant Toronto Style - hasn't taken over the architecture of major American cities, regardless of the occasional similarities in their buildings to some buildings here.
Incidentally, I see that the owner of Chicago's IBM tower, designed by the firm of Mies van der Rohe and completed four years after his death, is applying to have floors 3 through 14 converted into condos!