Three Hurrahs For Germany!
It can be taken by any country with a primary culture of North German or South German. The requirement is to own or have sphered all provinces with German cores. Luxembourg, Schleswig and Austria is however optional. It is also a requirement that the forming nation has 45 prestige.
Note that despite Ashkenazi technically is a Germanic culture, Israel is unable to form Germany and Ashkenazi will not be an accepted culture in Germany.