Hi!
First of all there is something that has caught my attention: "castilla, euskadi, galicia, and catalunya", why? Because you have mixed the names of this four regions in 3 different languages
The names in spanish (castilian) are: Castilla, País Vasco, Galicia and Cataluña.
In their respective languages: Castilla, Euskadi (or Euzkadi), Galicia and Catalunya.
The names in english: Castilia, Basque Country, Galicia and Catalonia.
Said this, I consider my country one of the richest ones in culture differences. Maybe I'm not the best person to talk about how different a catalonian is from a basque, but I may comment it from my point of view.
If you wanted to summon the main cultures of Spain I would say that you have just numbered some of them, perhaps the most known abroad. Almost every province (and there are 56 provinces) have a distinct way of being, customs, typical recipes and so on.
Moreover, inside each provinces the people are different (this is mainly because we are a very mountaineous country). From one valley to another, from one island to other, we are almost as different as a hawaian from a floridan. There are a handful of languages and dozens of dialects, accents and arcanisms.
In gastronomy, the south has it's own dishes, very different from ones of the north. Even in Andalusia it is different what they eat in Huelva, Cádiz and Málaga (and these three provinces are rather near).
It is unfair to generalise, but I may take some stereotypes to define the 4 regions:
Castilians are spartan people, galicians are rural, yet very friendly, basques are somewhat "obstinated", brute, they are delighted by a good meal, and they normally welcome everybody (in small villages they are very very friendly), and catalonians are hard-workers, yet somewhat "egoist" in monetarian issues.
Take in mind that cities are far from these stereotypes. People from Madrid are not really typical castilians, nor people from Barcelona are typical catalonians.
Best regards.
Fernando