What powers did the HRE government exert over the individual states within the empire?
HRE control over Burgundy and Italy was solid in the 10th century and nonexistent by the end of 12th. German states didn't really emerge until the first interregnum. Until then, they were just the property of powerful feudal lords. Imperial control was reasonably firm until the beginning of the Reformation. However, power within the HRE government was gradually shifting from the Emperor to the Reichstag; this didn't have to be a form of decentralization but it became one. The Reformation severely undercut imperial control and the Thirty Years War all but destroyed it. Protestant states didn't want to take orders from a Catholic monarch and everyone saw that the Emperor was helpless to stop foreign armies from crisscrossing Germany. After 1648, the HRE government was just a Hapsburg government by another name. German leaders might support the Emperor, but they didn't do it because he was the Emperor. They did it because the Hapsburgs bribed them or because the Hapsburgs threatened them.