My thoughts on the nations here:
Europe:
Great Britain & Germany: You practically hit the nail on the head with Britain and Germany. Britain is the top dog, Germany wants to be the top dog, they're going to butt heads sooner or later.
Aye. A fight will be unavoidable, but the intensity may vary, though, considering that Germany has not gone through Wilhelm II's reign (so far).
France: Sometimes I wonder if the Orleanists wielding Nationalism like that will backfire on them in the end game.
Perhaps, perhaps...
Austria-Hungary: it's essentially the zombie of Europe. Already dead, but holding on, primarily due to the beloved nature of its Emperor. Now while it is possible for it to reform greatly so, it's not like the Spains. While the Spains did have multiple ethnicities and most of them were already tied together, they were practically all similar (except for the Basques, but they've been content lately.) Austria's multiple ethnicities however as so vastly disparate from each other however.
There was a proposal called the United States of Greater Austria, that could have helped in there, but Franz Joseph's intransigence did not help at all.
Italy: The Irredentists also want Dalmatia as well. I wouldn't be surprised if Italian irredentism would also take them to take on other former Venetian holdings in the Eastern Med.
I doubt that would happen, actually. It would require a fall of the Ottoman Empire, and Greece would have a higher claim to those territories. And you have also given me an idea for the 20th century! So, thank you.
Russia: Hoping Russia survives, that is all.
They will, thanks to Aleksandr's reforms.
Ottomans: They're looking to die out soon, it might prolong its existence if the Young Turks and other Turkish Nationalist groups don't get to it.
Yeah, they are bound for death.
Corsica: Good for Corsica getting Tunisia. This is going to impress the Corsican nationalists greatly, although at great expense to the French and to a lesser extent the Italians (the irridentists want Corsica and Tunisia...)
Yup.
Sweden-Norway:Isn't Sweden-Norway going to be breaking up soon? (OTL they did in 1905)
Who knows?
Asia:
Qing: Well that depends on if the Boxer Rebellion becomes a thing, the Rebellion was the final death knell that led to the Republic.
I have something in the works for something that might actually save it...
Afghanistan & Persia: Assuming the battle lines will be maintained (Spain, Italy, the Ottomans, Germany, Austria-Hungary vs. Britain and France, Russia), the Great Game will be a moot point.
Yeah, but they are still relatively important.
Siam: I dunno...the reason Siam remained independent was due to then hostile relations between Britain and France, and Siam was a buffer (or rather, I think it was to protect French Indochina from British India) It being a Spanish protectorate is only looking for partitions across the board.
When they have Britain on one side and France on the other, with both of them friendly towards each other, the best chance of survival might be to call on someone that is opposed to both of them, instead of praying that they won't make a deal and decide to divide them in two.
The Americas:
U.S: I thought Manifest Destiny was all but dead at this point.
It could see a revival in the advent of Spain's growth as a power, and even then the Monroe Doctrine still exists. Though, I think that maybe I should either change the president from Thomas Reed to someone else, or establish that Reed's outlook has changed in the last thirty years to make him more pro-application of the Doctrine.
Brazil: Is Isabel ruling Brazil around now?
Yes, she is.
Argentina: Viva Virrientism, probably a very good way to establish itself as a premier South American power and rival to Brazil.
Indeed. Argentina could, hilariously, ally with the Entente as a counter-point to Brazil.
Chile: Well, at least the Second Chilean Civil War was butterflied away...so far.
Yeah. The situation changed quite a lot after the defeat in the Second Pacific War.
Colombia: Could there be an earlier U.S.-Colombian relationship?
I'm not sure. There could be an initiation of a relationship, but it was also the US that supported Panamanian independence when the Colombians didn't accept the deal the US offered.
Peru & Bolivia: This, could probably put another cramp on any Argentine expansion.
A revival of the Peruvian Confederation could be in the future...
Dominican Republic: Hoping for another foral region.
Hell yeah.
Africa:
Ethiopia: The sole Orthodox (and that's questionable) nation in Africa...If Italy doesn't do stupidity we could see it being a colony rather than a protectorate.
They count with Britain's protection, that prefers to keep them independent, so no, there's not much of a chance that Italy wins that without a war.
Belgian Congo: Welp, there goes the Free State.
Considering the travesty that the CFS was for humanity, I'd say it's an improvement. Of course, this means that
Heart of Darkness does not get written, at least not in the way it was in RL.
Egypt: Except Egypt was a protectorate, not a colony...or did the British decide to make it a colony and get rid of its monarch.
*facepalm* I have re-written that part to explicitly state that Egypt is a protectorate.
Madagascar: Hoping the House of Merina actually lives to see decolonization TTL.
*taking notes on how to derail this*
It seems that Germany (and by extension Spain) is in a good position in the probably-inevitable future land war in Europe. Whatever Thiers's flaws, he was probably right that republicanism is the form of government that divides the French people least; I can't imagine this restored Kingdom of France being utterly unopposed. The German Army is probably in good shape for the campaign against France for the same reasons as was the case IOTL, in addition to France's extra instability ITTL.
The problem for the Hohenzollern powers is naval; if it comes to war against the British Empire, they can't keep their colonial empires if their navies aren't roughly equal to the Royal Navy (OTL's Kaiserliche Marine wasn't even close), and the British IOTL were capable of navally out-building Germany alone without great effort and ITTL they'll probably be able to out-build Spain and Germany together, with greater difficulty but probably still success. It isn't reasonably in dispute that if US ambitions to end Spanish rule in the Americas end up in war the Hohenzollern powers are doomed, so they'd better tread carefully in regard to US public opinion. Will they? Only future updates will tell.
(In any case, the maintenance or loss of a colonial empire is hardly of great importance to a European power compared to the continued independence of its homeland; I'm sure that OTL's German Empire would have been happy to lose its colonial empire a million times over in order for the Kaiserreich to survive.)
Of course, all of that is presuming that there will indeed be a war, and unless Austria-Hungary and Russia wedge themselves into the system of alliance blocs (thus putting a trigger for general European war into the unstable Balkan peninsula) then that's not certain. But there's an element of narrative here; I doubt you'd set all of this up and then not have the great powers face off.
Good luck with writing more.
In first place, your analysis of the Spanish and German land forces is quite good. However, the situation in the Third French Kingdom isn't as bad as you imagine: their stability is a bit greater than you seem to imply would be.
As for the naval front, I would not write Spain and Germany off so easily. Yes, the British Empire can outbuild Spain and Germany put together, but Spain does have something over the UK: an advantage on submarine and destroyer design (plus some other things I'll show on Parts II and IV). Did you know that
the first destroyer was a Spanish design? The name for that type of ship actually comes from said warship. And, yes, I know that this does not mean handing Spain the "I Win" button, but it does provide a nice extra.
In regards to the US, given what I plan to do for the ATL Spanish-American War, they will be a bit likelier to join an European war. One thing about the land war on Cuba is that it was not as straightforward and easy as the Americans would like to think, and that was with the Spanish Army in there and in the Philippines being in the middle of a rebellion. Imagine what it'll be with the Cubans and Filipinos being loyal (more or less) citizens of the United Empire of the Spains, not to mention that the Spanish Navy will be much more capable and alert (no Disaster of Cavite!).
As for there being a great war between the European powers... there will be. A sad thing, but it was almost impossible to avoid. The actual trigger may actually not be in the Balkans, though. (Still have to decide how to start the spark, though)
Thanks for the support, and I hope you'll like the rest.
This WW1 will not be really easier than OTL. Spain might create a second front against France, but Russia is stronger, while A-H and Ottomans are not. So, the best strategy for Central Powers would be to convince Italy to join them, and defeat France as fast as possible. Even with the defensive focus of WW1 warfare, there's no way France can hold in three fronts against industrialized nations for too long. Then they can turn their land forces on Russia and win, hopefully before the US joins and secures naval supremacy and the loss of overseas colonies.
In parts, it might be even worse. France and Britain will have it worse in the Western Front (because of the two fronts), the Mediterranean won't be as accessible to the British ships as they hope (Gibraltar may not have enough defenses to hold off a determined Spanish attack), the British-French colonies in the Caribbean will be in danger because of Spain's strong position and those in the Pacific as well given Spain's friendship with Japan, but, on the other side, the Eastern Front will be more balanced (stronger, more powerful Russia), Spain's colonies in the Caribbean will be in danger when the US gets involved, and Africa will be a difficult affair (all of Spain's colonies will be bordering French or British colonies, save for Angola's southern border, shared with German South-West Africa). All in all, it will be a difficult thing for everyone involved ("Home for Christmas" might not even appear!)