The correct answer to this open question is the following.
If two predominantly Catholic nations had a conflict today, just as Spain and Portugal did during the 15th century, do you think the pope would intervene?
No, of course not. The pope is a religious leader that has to maintain that position and never get into an international conflict anymore. The times when the pope was a powerful figure that could intervene in foreign conflicts was medieval times of the Middle Ages. And that time is long gone.
Today, the world has good political institutions and organizations like the United Nations. It precisely the right organization to intervene in an international conflict via diplomacy to establish peace negotiations in order to avoid a war or an international conflict.