Here's a link to the spanish wiki -- it actually gives us some insight (not that its not obvious) as to what their motivations, and goals are in the game.

This is from what they believe to be the status of Spain:

Permanent advantage¶
one of the most profitable goods for middle distance trading are only sold in our terriotory ports, Seville and Barcelona.These muskets are particularly profitable to sell in Caribbian sea. So, we did our obligation to keep those carribian ports under our control (Spain has over 50% influence in all carribian ports) So this is our first key words 'firearm', 'muskets' and 'carib'.

high-end cannons¶
high end cannons (carronade14 and cannon14) only requires cannon(as goods), cannon balls, steels. And, cheatingly, Barcelona sells all of these! There are no other ports sell even two of them. They can be made from rower materials but takes much more time.

Situational advantage¶
now these are just advantages to us b/c we worked out the world situation to the way we wanted them to be.

Gold bar business¶
We prolly make money with golds more than any other nation. We have taken over Abidjan and St Jeorge in West Africa and unlocked gold casting recipe. We have a mechamism to make gold barp accessable to any Spanish who brings gold dusts in Carib. Plz send tell to Dary or Daryoon to find more details.We also have a strong military control over Caribbian ports. Our privateers go around the area to hunt down other pirates and privateer non-Spanish merchants to prevent their business & investments. (investments are done to ports with business chances. Bringing up risks kills business