A reply to /u/Cthulhus_Curios

So a few posts to get you started. What you need is to do some reading on the Eighty Years' War and Thirty Years' War, because the Iberian Union's history is essentially nearly completely dependent on those two conflicts.

• How did the Dutch Republic survive?

• The Spanish Armada in the Mediterranean and in the attempted invasion of England

• How did Portugal's empire decline?

• Portugal's secession from the Iberian Union

England went through a succession of rulers, which made significant changes in its relationship with Spain. France was initially largely incapacitated due to its Wars of Religion. The HRE was facing significant internal challenges that led to the Thirty Years' War. The Ottomans went through their ebbs and flows.

Feel free to read the above posts and if you have further specific questions about some of the countries I mentioned, feel free to post a question here!