Some linguists IIRC dispute classifying Galician as a separate language from Portugese.
Most people wouldn't think Galician was anything but a dialect of Portuguese if Portugal ruled Galicia. Although there would always be the Kingdom of Galicia (ruled by the Portuguese king) to remind people the region was technically separate from Portugal proper. But then again, no one speaks of the Algarve as anything but a part of Portugal despite the existence of the Kingdom of the Algarve(s).