[jltsiren]

Reconquista is an anachronistic concept here, but so are nations in the modern sense. Instead of looking at the wars in Iberia in isolation, it's better to consider them in the context of the wider Europe.

Medieval Europeans saw Christendom as the legitimate successor of the Roman Empire. (Or at least the elites did.) Many wars were fought to expand the borders of Christendom. Some of them against pagans, and some to take back land that used to be Christian. The wars that are often called the Reconquista were part of the latter.

So, in a sense, it was not about taking Spanish land back for Spain, but about taking Roman land back for Rome.