This thread is giving me a lot of needed education. Until recently I had thought that "Little Dixie" referred to the border counties (Vernon, Bates, Cass, Jackson). While reading Bruce's first volume I discovered that it actually refers to a different region.
As to Germans, I think the distinction is more on when they immigrated. We both know that there were German settlements in Spotsylvania and Orange County, Virginia, well before the Revolution. These folks became "Good Southerners". There is also the image of Toby McGuire's character in "Ride With the Devil". He came to Missouri from Germany as an infant, and had totally adopted southern culture.
The "Red 48ers" are a different matter. Many of them were on the losing side in the "Socialist" Revolution of 1848. They left the German States and spread all over the globe. Many came to North America, and totally changed the culture of the Midwest. These are the "Yankee Dutchmen". There was also a large migration of Irish at the same time.
In Texas, recent German immigrants suffered severe repression. I suspect that in Missouri the majority were strongly pro-Union and anti-slavery, but certainly there were some "Red 48ers" who fought for the South.