Might as well add in Asian powers to my previous list of countries' opinions on the two sides:
China wants people to get off it's lawn. Unfortunately for them, everyone (well, Europe and Japan) is still nibbling at it. Either side costs it to participate, but it costs about as much not to participate, so there's no reason not to get involved in some side in an attempt to reclaim something. If it sides with anyone, it'll probably join with the one power not to try taking it over - the United States (assuming it does join in).
Japan wants to be seen as an equal to the European powers. Therefore, it needs to get involved in one side or the other. In our timeline, it was a British ally, but this was built as an alliance against Russia. Given a more active anti-French focused British Empire, it's not improbable Japan ends up French allied instead.
Maybe bring up some minor powers too. Denmark and Sweden were both pro-Prussia, but neither was willing to get involved. Norway was strongly pro-British but neutral. With Prussia and Britain together (along with their biggest threat Russia), it wouldn't be unreasonable for them to get pulled in, though it's not impossible the different alliance setup makes them more pro-France than in our world. Belgium was being defended by everyone, and officially neutral as part of that defense setup. Netherlands had no allies, but relied on people not wanting their opponents to take its territory for protection.
So we're currently at:
Highly Probable Prussian Side:
Prussia/North Germany
Russia
Italy
British Empire
Highly Probable French Side:
France
Austria/South Germany
Japan
Likely Prussian Side/Neutral:
Denmark
Sweden
Norway
USA
Likely French Side/Neutral:
Ottoman Empire
Spain
Unknown:
Belgium (probably against whichever of France/Prussia gets the idea of attacking the other through it)
Netherlands
South American Nations
China
Neutral:
Switzerland
So, Europe looks a lot like WWI switching Germany and France and adding Spain to the Central Powers-equivalent, but in Asia Japan is on the opposite side. If I had to guess China would probably align with the United States, meaning likely Prussia. Pacific Theatre might end up getting interesting as opposed to everyone teaming up to get rid of the handful of German colonies in the area we saw in our timeline.
This list has a bunch of assumptions that don't hold up.
-- Britain is a huge question mark, depending on who is looking like the greater threat to the balance of powers. Calling Britain a "highly probable" Prussian ally is very much an over-hasty conclusion.
-- Japan siding against Britain? Guess again. Britain can actually threaten them. Japan will be 100% neutral if Britain sides with Prussia/Russia, and 100% with Britain if Britain sides against Russia.
-- Denmark is not "likely Prussian", because russia scewed them over. They'll be neutral until and unless Prussia is losing, in which case they'll jump on the anti-Prussian bandwagon in order to be rewarded with a mild border adjustment.
-- USA as "likely" on the Prussian side, too? No way. Neutrality until and unless American interests are harmed. If Britain sides with Prussia, you may see Atlantic warfare, and a Lusitania-esque incident may follow. If Britain is neutral or pro-French, the Atlantic is less likely to be heavily contested, and the USA will presumably just stay out.
-- The 'Unknowns' and Scandinavia are all bound to be neutral, unless attacked.
-- China is barely a factor to be considered. Assuming its history proceeds roughly as in OTL, it may join the Prusso-Russian revanchist bloc in a hypothetical Second Great War. (In which case we'll get the war Mackinder saw coming, in its archetypal form: the combined Eurasian Heartland versus the united Periphery.)
Anyway, this produces the following list:
Highly Probable Prussian Side:
Prussia/North Germany
Russia
Italy
Highly Probable French Side:
France
Austria
South Germany
[Rhenania, if it exists]
Likely Prussian Side or Pro-Prussian Neutral:
Serbia ("because fuck Austria, that's why")
Likely French Side or Pro-French Neutral:
Ottoman Empire
Spain
Denmark (neutral until/unless France is winning)
Neutral Unless Attacked:
Switzerland
Belgium
Netherlands
Sweden
Norway
USA
South American Nations
China
Unknown:
Britain
Japan (neutral, or pro-French
if Britain is also pro-French)
Portugal (follows Britain's lead)
Greece (likely pro-Prussian because anti-Ottoman, certainly if Britain is also pro-Prussian)
Bulgaria (likely pro-Prussian because anti-Ottoman, but may be in conflict with Greece and/or Serbia)
Romania (definitely doesn't like Austria, but doesn't like Russia, either)
....This is all an exceedingly long way of saying "Britain decides who wins this thing".