I don't believe that's the case- it just doesn't make any sense. Some of the best cartoon voice-over actors we've ever had work here in the states actually came from Canada, namely Henry Corden, Stanley Jones, John Vernon, Lloyd Bochner, Maurice LaMarche, William Shatner, Peter Cullen, Cree Summer, Michael Donovan and the list goes on. They've all worked well with the voice-over actors from here in the states, so the question of whether U.S. voice-over actors and their Canadian counterparts disliked each other is really irrelevant, considering the length of their work with each other in animation over the years and how well it has eventually turned out.