You know Voltaire's quote about the Holy Roman Empire being neither Holy nor Roman nor an Empire? Well, after the 100 years war with the HRE being one of the losers they split into catholic Austria and protestant Prussa. The reason why the HRE split in two nations (with other smaller countries breaking off too) instead of another country gaining their territory is because the HRE was already in an internal struggle due to the protestant reformation. From then on the Emperor or the HRE was a mere figure head.