As I far as I’ve been able to grasp the only tangible example of Siderno and Rizzuto really having problem, may be the death of Cosimo Commisso.

Vito himself was already dead, it seems like it may have been the alliance of HA and Rizzuto (ie. Wolfpack?), and Calabrese in Toronto, that are loyal to the system of business developed in Southern Italy (CN, Ndragheta, etc.) and it’s collective interests.

The divide in Ontario/Canada has to do with loyalty to either South Italy and everything from there, even NYC or those loyal to what is available in Canada, and their system.