I will go with whichever nation you all decide you want to start in. This is my list by priority and why.

1. France: I am American of French descent (dad) and am a Franco-phile. Also, the French had a reputation as being a strong military. They allowed their overconfidence to get the better of them during both WWI and WWII. That overconfidence should be aptly represented in our version of France.
2. United Kingdom: I am American of British descent (mom). English would make this so much easier. Not that we need to speak French in character.
3. Prussia: I speak German and respect the military professionalism of the Prussian elite.
4. Austria: I don't really care. They kill the German language...almost as bad as the Bavarians.