How is it that the Hapsburg House ruled over countries ranging from England, France, Germany, Holy Roman Empire, Hungary, etc... without any of these ever becoming unified empires? And how did a single house expand to cover such different regions of Europe?

/u/superfuels

This deserves a very long answer, but let me assume you are willing to do your own reading and challenge you with the following: How do rulers of the early modern era actually rule their domains? There was not yet a comprehensive bureaucratic body that we have today.

Let's start with a few cases.

How do rulers collect taxes and earn money? There were no comprehensive records of transactions and wealth. In the early modern era, direct and indirect taxes were collected through bodies such as parlements, churches, tax collectors. When it is done through parlements and tax collectors, they almost always had to advance the money the ruler asks for, and in return they are granted the right to collect tax. Membership in such bodies were highly coveted, as they often meant great riches and power. These all have specific rules of how they operate, and thus it was very difficult to unite entities because they were governed under different rules.
How do rulers change and communicate rules? This is the heart of the issue. If the direct control of a ruler was very limited, then the ruler had to rely on means to enable the rule, meaning parliments, nobility, churches, etc. How do you get them to unite, if they had developed different rules over the centuries?

If you want to know how the House of Habsburg came to control a ginormous domain, look in the FAQ section on the sidebar, this has been asked many times.