In OTL, the main Spanish fleet, against the advice of its commander, Admiral Cervera, was sent to the West Indies to confront US forces.
At this time, the fleet consisted of the three armored cruisers of the Infanta Maria Teresa class plus the armored cruiser Cristobal Colon, plus two destroyers.
One of the Maria Teresas, Viscaya, was in bad shape, desperately needing a docking after a long period of cruising, and the Colon had not yet had it's main armament installed, leaving it only with secondary batteries.
Sending them to the Caribbean was essentially a death-sentence, which the fleet was aware of and was probably not the best morale-builder. There were no safe bases to operate from, and Cuba is too close to the centers of American power to use as a base.
Cervera wanted to base the fleet in the Canaries and threaten all US moves on Cuba with his very presence, possibly striking at New England to create panic (to divert US naval resources - and it would almost certainly have been very effective), possibly attempting to intercept USS Oregon on its arduous trip from San Francisco to the East Coast, and waiting for reinforcements by ships that were under repair or completing.
These included the battleship Pelayo which was rebuilding in France, the huge armored cruiser Carlos V, four modern destroyers, and a large number of auxiliary cruisers and support vessels. In addition, Colon would have had its main battery installed, and Vizcaya brought up to full fighting-trim. In OTL, it's hull was so fouled that it's speed was lowered by several knots, which was catastrophic at Santiago.
That would mean:
1 BB Pelayo
1 AC Imperator Carlos V
3 AC Infanta Maria Teresa
1 AC Cristobal Colon
4 Protected Cruisers
6 DDs
5-6 torpedo gunboats
That's a pretty respectable force. While not a match for the USN, it would have been very difficult to maintain a blockade of Cuba and protect invasion transports with a fleet like that lurking about. The US had practically nothing in the way of destroyers or torpedo boats, a fairly significant advantage for the Spanish.
The USA had four good battleships, one 2nd-class BB, two good armored cruisers, a lot of really sad protected cruisers, and no destroyers:
1 BB Iowa
3 BB Indiana
1 BB Texas (2nd-class)
1 AC Brooklyn
1 AC New York
18 Protected Cruisers (of which 5 were decent)
In addition we had a few monitors and a gigantic quantity of auxiliaries, including large fast yachts, liners, armed tugs, and auxiliary cruisers, as well as all sorts of support ships.
If Cervera had based himself in the Canaries, bombarded Boston or Portland, and struck at blockading forces, it could have unravelled the US war effort.
As it was, the whole Eastern seaboard was demanding protection against the Spanish, which was a naval drain; if the Spanish had actually bombarded an Eastern port, we would have been forced to detach major units from the fleet.
Blockading forces would have been in a difficult position; there are a lot of ports to watch, and no individual blockading force would have been a match for the Spanish fleet. That would also have made it difficult, if not impossible, to land and maintain an expeditionary force.
Intercepting Oregon would have been a serious longshot, but if accomplished would be a huge blow to the US.
What do you think?