Taft was killing the economy of the Midwest by getting rid of agricultural subsidies. That's why the states flipped to the Democrats in 1950 and 1952. Do you find this plausible? After 1952 I suspect the region will go back to the Republicans for the reasons you mentioned.
Honestly no, I don't see them vote Democratic after Morgenthau ever again. Most of the Germans and their ancestors in the region have arrived after 1845, it means that there's still a whole lot 1st generations immigrants alive, but also most have grown up either speaking German or having relatives speaking the language. Their churches are connected to the homeland, which mean we likely have seen charities to help their relative in Europe, many still have or had contact with their families, and they likely have received letter begging for aid and tales of dead or disappeared (often emigrated) relatives (remember that West Germany have lost 1/3 of its population, and the American Zone have likely been the centre of this loss with half having died or disappeared). Their young men have served in the occupation and bring horror stories, many have likely married German women, often just to help them escape the hell hole West Germany have become. These people may not vote republican, but it snow in Hell before they vote democratic again. It's more likely that we see a regional party develop (it could be called Farmers party, Farmer and Workers Party or maybe just Labor) in opposition to the Republicans.
In fact I think it could be a interesting aspect of this timeline, that we maybe see the permanent development of regional American parties and we likely see a weakening of the American presidency, especially after a unelected president have run his own private genocide.
Agreed. How might this impact apartheid?
It could go both ways, but looking at South African demography, I have a favoured theory. In the Cape Province and Natal, Coloured and Indian (Asiatics) was the second biggest in minority in each. While Whites was the 3rd biggest with a few 300000 less people in Cape and some 40000 in Natal. Here Whites become the very clearly the largest minority group. But in both provinces their primary languages (Afrikaans in Cape and English in Natal) become threaten by the influx of third European language. But the Coloured in Cape was mainly Afrikaans speakers and the Indians in Natal used English as their main public language. So I think that with White dominance secured by the German immigrants, we will see full citizenship and voting rights be given to Coloured and Indians. That expand the ruling minority of South Africa with 10% (lower than historical thanks to the higher population) and potential more (as more Asian immigration will be allowed and intermarriage will become legal again). So we will fundamental get a ruling minority by 1990 which make up 33-40% of the population with Cape likely a "Afrikaans" majority. Also we will likely also see some Black with Afrikaans or English as first language will be seen both by the general public and legal as Coloured
The result will be that Blacks can be easier be kept down, but it will also result in South African being much richer, and some of that will likely drip down to the Black population, and with intermarriage being legal plus assimilation possible, we will likely see a increasing Black urban class (mostly workers but also professionals) plus farm workers getting full citizenship and voting rights. It's important to remember that discrimination of Black in Apartheid's ideology wasn't based on them being Black, but because they belonged to Bantu nations, which was a primitive proto-nation, which needed to be uprised to the same civilisation "level" as the Afrikaans and British nations. Here the Afrikaans have already recognised non-Whites (the Coloured) as part of their nation. As such I could see them expand this, especially if the Black person can find a White or Coloured ancestor (which I think most will be able to find, especially among the Zulu and Xhosa)
A few extra thought about Denmark I think Bornholm will become a independent province (likely as unified Province-County, which is likely how Faroe will be set up too). Also I looked up Danish demography. When I looked at that I got some interesting conclusion. A poorer Europe will mean a poorer Denmark, a poorer Denmark will mean that Denmark upkeep their high post war population growth longer (3 children per woman in 1944-46 falling to 2,5 child by 1950 and staying that high until 1968, after which it fell to 2,1 by 1973 and then we saw a collapse down to 1,4 beginning with the oil crisis lasting until the mid 80ties where it began a slow rise, where it hit 1,9 by 2008 and fell again with new crisis to 1,7 and began a new slow rise ). My conclusion are that with the greater chaos in Europe, we will see the high birth rate after the War last longer maybe even rising higher (3,5 is not unrealistic), while it only fall down to 2,5 between 1955-60 and stay there longer. Without the degree of prosperity we saw in ours 60ties we will likely see the birth rate stay high, also with the German population surplus of guest workers, Denmark are also more likely to import more Germans workers to the post-War industrialisation rather than rural Danes. So the Danish population stay much more rural, while most cities and towns get large German minorities. The result is a higher birth rate. So my guess is that Danish population (including Holstein will develop this way) 6 million 1945, it reach 7 million by 1960, 8 million a decade later by 1970, after it reach 9 million by 1980 it begins to slow down hitting 10 million by 1995 and slow even more down after that (of course the development after 1980 depend on a potential oil crisis, because Denmark have access to North Sea oil, we have high growth after the technology to extract it have been developed and the prices have been high enough that it was economical).
Around a fifth of the population is likely to German speakers while around 5% will speak North Frisian (this is much more than historical, but I think we will see great damming project of the Wadden Sea where they live).
I also see some interesting developments in Sweden and Finland, Sweden got a a several hundred thousand Finns after the War (50ties and 60ties) as guest workers, around half was Swedish speaking Finns. Here Sweden likely get around half a million German refugees, and continued immigration later. This mean less need for Finnish workers, but also less need for rural Swedes to move to the big cities. My guess Is that Swedish population will end up something like this 8 million people by 1960, 10 million by 1975, 12 million by 1995.
At the same time Stalin will likely demand less reparation of the Finns, if he can get Norway, Sweden and Denmark join into a union with them (as it would make Denmark and Norway neutrals). The result are less impoverished Finns, while Sweden at the same time have less need for Workers. The result is a higher Finnish population. Likely something like this 5 million by 1960 and 6 million by 1995. At the same time the Swedish speaking group will likely stay much bigger I think around 8% of the population by 1995 (rather than 6%). Vaasa (Swedish Vasa) will likely have a Swedish speaking majority, making the region Ostrobothnia even more the mainland stronghold of the Swedish speakers (today they're only half the population because of Vaasa)
A few other thoughts about the German diaspora. The vast amount of Germans exiles in USSR will likely survive, we will likely see a male surplus (women will likely not be send as "guest workers" to USSR). At the same time USSR have a large female surplus (mostly Russians, Belarusian and Ukrainian). So we will likely see them ending up marrying locals. The children was usual counted as German historical and the German group made up around 1% (3 million) of the USSR, with Northern Kazakhstan and western Siberia (the fertile area on the border of Kazakhstan) being the main German population centres (with Germans being 6,5% of the population in Kazakhstan at it highest in 1970). A large amount of the Germans historical didn't speak German any more by 1990 (likely half), they was in general discriminated against. Again Kazakhstan and Siberia was the stronghold of the German language (there's still 400000 speakers in Siberia, mostly descendent not of people exiled there, but mostly German farmers settling in the area under the Czars, and they have mostly be left alone since (it's hard even for USSR to see impoverish Siberian farmers as class enemies)). There was talk about about creating a German SSR in Kazakhstan in the 80ties. Now with some context given. Germans will likely be a much bigger group in your story. I'm guessing we will see between 9-12 million people be identified as Germans by 1990 (I keep using 1990, because the development of USSR will clearly be different from historical, so I need to see how USSR develop after 1990 to make demographic guesses after that). Western USSR will likely be home to many more of them than historical. But we will likely also see a much higher population of them in Kazakhstan and Siberia (likely double, which is till only something like 2 millions in Kazakhstan and 1 million in Siberia). I also think that while they're discriminated against, they will still embrace the ideal of a Soviet people. So while they're a separate group from Russians, they will de facto count as Russian when we talk about keeping USSR together.