After World War II? Probably not.
The real hard part is getting Newfoundland independent again at all post-World War II, considering how important US military bases were to the economy at that point. Even if you butterfly away Smallwood and you don't get a confederation option on the referendum, Newfoundland at this point hasn't had responsible government since the Depression and is still run by the Commission. They're answerable to London, and London's not going to allow "independence" as a referendum option.