Is that it would insult the King of Portugal really relevant The King of England called himself King of France until 1801 and still managed to have long periods of good relations with the French What bad relations there were had little to do with that One might note that Italy always referred to the whole of the peninsula but that the Kingdom of Italy only covered the northern part of said peninsula That the king of Castile might have called himself sometimes King of Spain is not a surmise refuted by stating that Aragon and Portugal might also be referred to as Spain See e g here which shows a papal official in 1504 using Rex Hispaniae for the king of Castile