I agree that a Spanish hold on Ireland would likely have been very tenuous and short-lived for lots of reasons, distance and the deterioration of Spanish leadership by the late 17th century from its height of perhaps a hundred years earlier would all have conspired against an adequate foothold in Ireland.All calculations need to consider:
In short, any fantasies of Spanish-controlled Ireland, and some golden age beneath the strict control of Salamancan priests, is for las Aves (in both senses).
- why Elizabeth's non-navy was able to see off the Spanish fleet (not least vessels more suited to northern waters, and those mass-produced cannon from Sussex iron-masters);
- why the Agricultural Revolution in England spawned an industrial one (spare labour, the coincidence of coal and iron at the very moment when coal technology was taking off);
- why England, from Scottish know-how, developed sources of energy (i.e. steam technology);
- why England adapted and exploited Dutch liberal-capitalism;
- why other national economies across Europe didn't;
- why North America went Anglo-, not Latino- (which also meant no London-based power could tolerate foreign interests sitting a-top of Atlantic trade routes) and
- why Spain, of all contenders, was floundering by the seventeenth century, and effectively a failed state by the nineteenth.
They did have a tendency to paint a red cross on their sails and hope for the best at times, their military and navy was stuffed with minor sons of the nobility and every promotion or mission granted from the court was a political nightmare.
It is arguable that the finest victories the Royal Navy ever had were led by commanders who had merit as commanders, whether like Cochrane they had come in through the hawse-hole rather than by patronage, meaning they end up as Admirals having been Able Seaman when they started out.
It can be argued that as soon as the qualification level to be able to stand a watch as an officer changed from being examined in seamanship by a sitting of Captains at the Admiralty to pass for second Lieuftenant on a Royal Navy vessel the requirements changed around the end of the 18th century and a young lad had also to 'pass as a gentleman' that a similar deterioration began in the Royal Navy, away from merit and toward social standing.
This would have meant Nelson would have scraped past as the son of a Norfolk landowner and some schooling whereas Cochrane would not have passed and would have remained a Master at best. And there is a school of thought that said Nelson was a fine leader of men (the 'Nelson touch') whereas Cochrane was a sailor's sailor and great tactician.