Confederate Kentucky. If you're going to do it, please address the reasons why it didn't happen in OTL. It wasn't just the CSA violating Kentucky's proclaimed neutrality. Even before that the state had voted to remain in the Union. People along the Ohio River, which was the most densely populated part felt a great deal of kinship towards the midwest, especially Ohio and Indiana and to a lesser extent Illinois. Also Louisville, like the midwest had a large population of ethnic Germans. The feelings of the mountain men in the Appalachian part of the state were similar to those of the mountain men of what would become West Virginia. Those more sympathetic to the Confederate cause came from the southern half of the state, closer to Tennessee.
More united Germany. Includes Austria. Presumably Lichtenstein and Luxembourg too, but Austria's the big one, especially if they also get Sudetenland with it. You have to somehow address the
Hohenzollern vs Habsburg issue. The strong male preference in semi-Salic inheritence makes this difficult to do by marriage, not to mention the Protestant vs Catholic issue. You'd have to have one of them be subordinate to the other, have them go republican, or if going the marriage route have one or both adopt a system of inheritance with less male preference and have someone convert or otherwise reach some arrangement over the Catholic vs Protestant issue.
The notion that trade makes warm fuzzy friendships inevitable. It doesn't. It can certainly help, but it's no guarantee. Taft tried that with dollar diplomacy. It was a failure. Some people will point to American trade with Britain and WWI. Although Britain was the USA's biggest trading partner at the start, their 2nd biggest trading partner (before the near-total blockade) was Germany. In the present day, the USA and China are each other's biggest trading partners, and most certainly
not close friends.
Speaking of Germany, I hate it when they're seen as just a bunch of proto-Nazis, no matter how far back the setting or POD is, or the notion that a victorious Imperial Germany can't liberalize.