Hope the writing is going well. I've again made a belated attempt to see my ideas of the story.
Depending on exactly how powerful the monarchy is in Italy, I could see the Civil War erupting out of tensions between Communalist groups & organised crime. In 1928 A "moderate" is elected as Prime Minister, portraying himself as an honest man fighting against the political fringes with only his charisma. Once in office, he realises that his lack of political ties to corrupt groups is a liability to his power, & starts working to expel corrupt influence to replace it with his own. This leads to mass (paid) protests over the "Communalist tyrrany" the PM is imposing on the Italian people. In response, this nameless figure declares himself an avowed Monarchist & works personally with the King to keep Communists out of office, while at the same time fighting corruption. In response, the Communalists rebel. Prussia, being on the Communalist front lines & never missing a chance to use their army, opens up a second front to stall the offense & buy the other nations time to join in the fun.
Thanks! Unfortunately the busy week caught up to me before I could finish, but be on the look out for sometime later this week if all goes well
In regards to Italy, the Italian Empire (Imperial Union of Italy) is a more more loosely held together entity than our OTL version...think OTL German Empire but even more powers to the individual parts. The Emperor himself acts more like a Prime Minister in many ways, so there isn't an actual PM position ITTL. Not as you're thinking of, anyway.
The main problem that Italy will face is that the South rejects communalism, where as the North starts to embrace it, and there are attempts made to end monarchy in some of the individual states. One succeeds in doing so by referendum in 1928, and this leads to a showdown with the "central government" and the other constituent Italian Kingdoms, and war ultimately breaks out (also leading the other communalist-leaning states to oust their kings as well).
I imagine the Federalist candidate (Secretary of State?) would take a pragmatic approach to the war, while the Liberal candidate would put it in more idealistic terms: "The only wars America has ever fought were for freedom & democracy. The Dixians tried to pervert this fact for their own gains, but the Cornelius Roosevelt resisted. I intend to carry on that Liberal tradition. May almighty God continue to bless the United States of America!" Of course, this would all become moot once Gibraltar happened, but it was a nice gesture. Perhaps the Liberals could add an Episcopalian on the bottom of the ticket. (Which flavour of Episcopalian is your choice.)
It's still too early to tell for sure which party will have the Presidency for the most part. That usually becomes more clear as the details fill in and the decades get fleshed out. So I could change that and a Federalist win instead...other than the fact that the Nationalists and Federalists have been in charge at this point (1930 election) since J.P. Roosevelt won the 1918 election...seems like it's time for the pendulum to swing back?
And correct, the Gibraltar incident will essentially "torpedo" all but the most ardent pacifists, and whoever IS POTUS will have no trouble getting war declared.
Not sure what you mean by "flavor of Episcopalian"?
I suspect that one of the opposing parties would draft a Lutheran German-descended Governor as a "peace candidate". This would fail, of course, ending Prussia's last real hope of survival. Britain will strenuously object to the UER annexing anything but Prussia, proposing everything from an Iberian Union to a renewed Venice to that end. However, their appeared hostility towards Communalism is made up for (mostly) at Rome, where the UK proposes the use of the city as the HPCHQ. The US is happy with Spain & indefinite peace.
Prussia is going to be a mess by the time the war is over. It is *somewhat* popular at the start, but that quickly fades, and by the end of the conflict the nation is tearing itself apart. UER will come in and help restore order, working with local communalists and liberals to help bring about the transition. There will be some rejoicing about "bringing all the Germans under one roof," but only so much. The Holtz Terror will have ended (he's going to step off the mortal coil in 1926 and by the end of the war most of his supporters will have been purged out and his opponents within the Party will have taken control, though most real post-Holtz reforms will not kick into full gear until after the peace).
I imagine the Liberals would be hampered by the CPUS complaining over the States' complacency at the negotiating table & their lack of reproach towards the UK. This would sufficiently split the left-wing vote that the Federalists win the office. The trade union is a small wink at Britain, who can freely trade items to the US through Borealia. As another concession to the UK, the administration decides to leave Spain to a monarchist government. Of course, this backfires. One newspaper proposes in jest that the US should have given the Spanish mandate to Mexico.
I hadn't actually thought about how the UK would get special treatment with NATU, but that is likely what would happen. Good call there.
After losing the past four runs, the Nationalists would have to be innovative, using the first campaign to advertise on TV (or whatever it's called ITTL). They state that the Federalists were abandoning Spain for the UER to take freely, & use the conservative resistance to this nonexistent left-wing threat as a metaphor for America in '48. The fact that the Liberal party's frontrunner was killed by a Communalist radical didn't hurt either.
The UER would be rife with intrigue, both with its allies & between members of the same government. Naturally it would invest in technologies to transmit & decode messages. The creation of the computer was a happy accident caused by this.
King William may well have visited Tampa Bay when it was returned to the US, which could have gave him the BUN idea. The Colonial Commission would likely be added in by Home Rule proponents in Parliament.
I hadn't considered how long of a loosing streak that would be for the Nationalists. All the more likely that they would win the '48 election. I like the idea of them seizing the new medium of TV (which would definitely be new but more prolific than it was OTL at that time). Not sure what I think about the assassination of the Lib candidate, but I may hold on to that too.
The UER will be a mess in the late 40s, early 50s, as the Union goes through a "de-Holtzification" a la what happened OTL in the USSR after Stalin died, but more so. Holtz is publicly repudiated by the Party as an out-of-control radical that nearly broke the Union. Kommunalingua will have made enough inroads that it doesn't go away, but there's no longer the official push that everyone learns it. The anti-ethnicity campaigns will end, and the Union's cultural diversity will be celebrated, instead of trying to make everyone the same. All this on top of trying to integrate Prussia and other territory. By the late 50s, the UER will be in a bit of a cultural revival.
King William will have be Prince William Victor when he visits with his mother, Victoria III, for the official handing over ceremony for Tampa Bay in 1938, yet another sign of Britain and America's "special friendship." A little early for him to be inspired for BUN I think. Though I could see him being a good-will ambassador for his mother and visiting all parts of the Empire and getting the idea for change.
A Nationalist-Federalist merger seems too similar to the Democratic-Republican merger. I would propose a system more like a three-party system, where perhaps the Federalists & Liberals join one ticket (while still remaining decidedly separate in Congress) & the CPUS (with their belief in strong government and smaller government units) being the minor third party that can still be an important factor. Until 1960, that is.
That did occur to me, that the merger will feel too much like previous ones. However, I don't see the Feds and Libs having as much in common as the Nationalists and Feds would. I haven't actually worked out the exact mechanisms for the CPUS will win Washington House in 1960, just know that they will win.