Vito was made in Canada, into the Sicilian mafia, not the american. They were technically under a Bonanno flag, but loyalties were always with Cattolica Eraclea.
He was never going to take orders from what he and his family (the Rizzuto family blood and mafia) considered a group of thugs and glorified rats, which is how they looked upon the American mafia.
Even in the 70's/80's?
Especially after he was passed over for UB, he started to work more and more independently from Cotroni and Violi, doing things on his own, not asking for permission, etc.
