Just two surprises for me on the GDP list:
1) I did
not think the USA would head the list, because I figured the United States had to have gained something from its imperialism of OTL, therefore a not-insignificant part of our economic leadership OTL has to be due to having grabbed what we have not grabbed ITTL. Not so much the formal colonial possessions--Hawaii, Philippines, Puerto Rico and Canal Zone--but the informal dominance in places like Cuba and pretty much the whole Carribean and Latin America in those latitudes, getting toeholds in China, that sort of thing. Without what we extorted by force in this manner, it seemed to stand to reason that we would not be as rich. Still I would think among the leading five nations, perhaps when the first one is as far ahead as Germany is here, then number two, but not number one.
However I can see how the counterargument could run--as Jonathan says, we didn't shoot ourselves in the foot with a Great War (well, not
both feet--I think the Latin American misadventure of the 1910s involved shooting off a couple toes on one of them--and actually did, apparently, result in just a bit of that greedy hegemony of OTL sticking to our fingers, in Nicaragua...
). Sitting pretty as neutrals in the Great War was an opportunity; the growth of the colonial possessions into self-interested and assertive entities that may or may not tear loose from their metropolis but certainly will only stay based on gratification of local interest means that Americans coming offering good deals will not be shooed away in the name of imperial autarky and preference in every case--so there are ongoing opportunities despite the world being formally sewn up. And there are outright independent powers to trade with. Thus, despite a failure to secure informal imperial puppet strings of our own, opportunity is open for middling honest American business people, and with it honest profit. Given the vast domestic market of the USA which even OTL predominated over global concerns in US business circles at this time, Americans would hardly be drastically worse off. Whereas for a European power to match and surpass American standards of living for their average citizen, they would have to become so wealthy that it offsets the rather medieval conditions some classes of people and some regions have long been mired in. Note--Jonathan has not clarified yet whether Germany has gotten rich by raising everyone's standards, or by an even more drastic polarization than existed before, where a handful of new business aristocrats share wealth on a scale scarcely known to humanity with the other handful of old aristocrats while the poor have scarcely advanced at all.
Now this timeline being what it is and Germany having the nature it had last time we looked, I'm betting on a semi-fair outcome, with the "rising tide lifting all boats" in the Teutosphere, so indeed the rich remain significantly richer, but the working-class Germans also enjoy prosperity unprecedented to them and quite on a par with the average American, or nearly so--this thanks to very assertive unions and lefty political parties they vote for. These parties may not have representation in legislatures and executive government in proportion to the votes they win, due to openly biased vote discounting mechanisms adopted explicitly to keep the commoners from running thing--but if that is the case, the upper/middle class alliance that rigs it that way had all the more better yield on bread-and-butter issues to these masses, lest they be driven to open revolution.
Which brings me to 2)
2) Bohemia is my biggest surprise in Europe. The Protectorate or whatever it is called is hardly mired in poverty of course, it is at least at the European average and perhaps well above it. What it is not, is on a par with Germany. And that's what I would expect! OTL Bohemia was a prosperous, major industrial center despite being under the control of Austria; being under Berlin's management I'd think the Czechs would have been swept up in the rising tide quite as much as any other part of Germany.
That they evidently have not is ominous for the peace of the German possessions. You've already mentioned trouble in Poland ahead; I figured however that Bohemia would stay with the Germans. But here, I see a sign that perhaps they'd rather aid their fellow Slavs; perhaps here even a Czech-Polish union might not be out of the question!
Because quite evidently, it would seem that when the Germans, acting in a public or private capacity, had tough choices to make that meant someone somewhere would suffer and not benefit, they passed the rotten egg onto the Czechs. And Poles of course, as I'm afraid I cynically expected. It would seem that the Slavs under German direction are all treated as second class, and their growth is stunted.
That being the case I fear Germany would be far more ethnically polarized than I hoped. I expected the Poles to be troublesome, defiant patriots no matter how well the Germans treated them--therefore the Germans would tire of doing them favors and Poland would inevitably seek to break free, at any cost. But I thought the Germans would be more businesslike and fair in their dealings with Bohemia and that the Czechs would respond well, becoming an integral and valued part of the German economy and political nation, though not of course ethnically German. But it would appear not, and this bodes ill for continued and extended German hegemony--sadly, super-rich and super-huge Germany may well fall on harder times soon.
Thanks to their own shortcomings of course.
Now these statistics don't tell us anything about regional disparities within the nations, which are probably very significant; I expect the American South is as per OTL distinctly poorer as a whole than the Northeast and Midwest for instance--though I also expect it is less so than OTL--but in turn that much of the greater Southern wealth that raises it above OTL regional averages is because Afro-friendly regions are mostly (though not all!) very significantly richer--the Carolinas, South more than North, and Sequoiah are where I have in mind here. But also a slight elevation of the whole South--but despite the near-parity of the Carolinas and Sequoiah with Northern standards, the South is still, I would imagine, poorer than the North.
In Germany too, Bohemia might stand out only because it is not aggregated with the rest of the Hohenzollern Empire; there might be parts of the wholly German lands that are also left behind. But this must mean that other parts are even richer, quite on a par with the USA or even richer still. Perhaps the Bohemians won't feel as alienated if they are in the same boat with other Germans. However, Bohemia clearly has more potential than some of those other regions, and if they aren't averaging with Germany as a whole it means the Empire has dropped the ball developing that potential.
And things could be worse in Bohemia rather than mitigated, if the depressed average of Bohemia resolves into Bohemian Germans--presumably not merely Sudentenland residents but residents in the central cities as well--who do quite as well as the German average, versus Slavic Czechs and others who are all the more seriously depressed down to average European levels or even lower. It would be bad enough for residents of Bohemia to be less well off and feel they are given scanty seconds, but if it is clearly a case of Germans being favored and skimming the cream off of a more deeply repressed Slavic native population--that is a downright explosive mix.
I know the timeline has veered away, to an extent, from the characteristic OTL development of ethnic and racialist consciousness in favor of a less-neat-on-paper political eclecticism that puts more weight on religious affiliation--which is why I had greater hopes the Germans would overlook the non-Germanness of the Bohemian peoples and focus instead on their affinity for a Germanic attitude to business. As for religion, they are Catholic, which is a liability in dealing with the house of Hohenzollern, but should have tied them to the Catholic southern Germans. If however the Slavs of Bohemia feel downtrodden as Slavs (or perhaps as Catholics, if the Catholic Germans are also below the national averages as they might be) then I suspect a turn to a Polish alliance in separatism might be in the cards, since no one is more Catholic than the Poles! (Indeed, the Poles might look askance on aligning with Czechs and Moravians because they might seem too liberal Catholics--but then again the Polish patriots would probably include a lot of radical progressives among them, as per OTL--who might regard Bohemian Slavs as too bourgeois!
)
In the worst case for Imperial Germany, the southern Catholic lands, German and Slavic alike, might
all be alienated, and looking to ditch Berlin.
But I suppose I ought to take a less impressionistic look at the statistics, and get a better sense of relative magnitudes. If Bohemia is poorer than Imperial Germany aggregated as a whole, is it perhaps still on a par with its southern German neighbors, and are they, though poor compared to North Germans, still doing very well compared to their non-Imperial neighbors? They might have no desire to break loose but a strong one to get more of the Imperial pie for themselves, but at the end of the day count themselves lucky to be within the Imperial system and not outside it.