For almost a thousand years, the Roman Catholic church was the unifying structure in Western Europe. Although it was not technically a political organization, it wielded tremendous political power. This authority went far beyond the boundaries of the Papal States. At a time when Europe was a collection of fragmented kingdoms with weak monarchs, the Roman Catholic church was virtually unrivaled. It could and did dispose kings and rearranged kingdoms according to the will of the Pope.
Obviously, this power brought the church great wealth. Unfortunately, this wealth led to corruption. By the time of Martin Luther, the church was a shell of its former self. Luther began by calling for reform within the church. The church naturally saw Luther and others like him as a threat to its power. Rather than accepting the reformist ideas, they condemned the reformers. This alienated adherents to reform theology and, contrary to most of their original intentions, forced them to reject the church and its teachings altogether. Conversely, the reformers then had to come up with their own theology and set up their own churches.
Such was the rise of Protestantism. For many nobles, converting to Protestantism was a way to get their hands on church lands, to stop sharing tax revenue with the church, and to assert their own independence. The Holy Roman Empire in particular saw a lot of conversions from Catholicism to Protestantism (and sometimes back to Catholicism) for political gain. It took a series of wars between Protestants and Catholics to determine who whether noble converts could retain their lands when they converted.
Within a few hundred years, two methods of state building dominated the political landscape of Europe. These were both largely the result of this split between Roman Catholicism and Protestantism. In some countries, like England, the monarch assumed the power that the Pope used to have over religious matters. This helped strengthen a sense of obligation to the monarch in the eyes of the citizens. Eventually, this idea would led to an idea of nationalism. In other countries, like Spain, where the Monarch gave his full devotion to the Pope, the countries Catholicism became an important source of national identity.
Some countries, like France remained very Catholic, but the king felt comfortable with ignoring Rome's opinion on many political matters. French monarchs ended up giving Protestants many more concessions than the Pope would have liked, although the country as a hole remained strictly Catholic. Thus we see that even in some Catholic countries, the post-Reformation climate left the authority of the Pope in question, even in the eyes of the loyal. In those countries were many converted to Protestantism, the power of the Pope was forever broken.
