Just (hopefully) a quickie for the Spain related achievements, do I need to unite Spain or can Castille do them just as well?
Pretty sure that if the achievement says "Spain" you have to form Spain before it counts. Some other ones require that you not form nations. There are also some that require specific start nations. If you are familiar with the code you can check them in the EU3/achievements/achievements.txt file.
edit: actually, upon further review, both the discover America and Spain is the Emperor achievements have Cas or Spa triggers so can be done as Castille