The correct answer to this open question is the following.
During the High Middle Ages (100-1300), France and England formed unified states while Germany remained divided.
This happened because the governments of France and Great Britain created vast kingdoms that increased the power of control in some European regions. And this was the result of solid leadership in each of the kingdoms.
The problem in the case of Germany was that it never has a true leader -as was the case of France and England- who could be recognized by all the tribes. No leader was strong enough to unify the different territories in Germany.