OOC: This is really unlikely for two reasons. If you change the reasons, you have a very different universe.
The teams for the separate realms in the UK is a rather dubious privilege or tradition granted to the English because the sport was invented there. So for a start, in this universe, soccer/ association football has been invented in Spain.
Second, the realms within the United Kingdom kept their separate identities much better than they did in the unified Kingdom of Spain formed by the Bourbons about the same time. So when international tournaments start, Spain is much more centralized. In particularly, Franco would NOT have allowed the Catalonians their own team, let alone the Basques. So you have to change much more Spanish history than the OP probably thought.
Also, how many players in the Spanish team that won the World Cup not come from Castille? This might not affect the World Cup much at all.