It wasn’t just the printing press. If I had to place any event as the source of the Reformation it would be the fight between the Papacy and the HRE over who controlled the crowning of the Emperor.
That set the stage for a long drawn out fight between the Catholic Church and Empire, and resulted in the political situation where both sides saw Luther as more than just a monk asking questions. He became (and to an extent remains to this day) a focus of all the hopes and hates of the time (similar to the view the English had of the Pope post Henry VIII).
In reading Luther’s words, he was a bit surprised for all the fuss made after the 95 Theses. Now, he was a German and grabbed the ball and ran with it the direction he felt he had to, but a split was not his desire (and doesn’t remain a desire among most Confessional Lutherans).
The printing press expanded things, but remember the Cathar’s predated the press, yet it took a couple decades of war to stop them.
Also, important was the fact that if there was a "national church" (i.e. the Church of England), the government would have a lot more say over what happened with tithes and property.
The emerging European nation states DID NOT want to be subordinate to the papacy and there were only two ways to accomplish this: The first was to be so strong militarily and economically that there was nothing the Vatican could do, this was the method employed by France, Spain and the southern portion of the HRE. The second option was to get rid of the Catholic Church and assume control, this was employed in the northern HRE and England among other place.
The printing press expanded things, but remember the Cathar’s predated the press, yet it took a couple decades of war to stop them.
True, but very few people outside the region really knew at the time what the religious views of the Cathars was, they only heard the "official line" from the Church. The printing press made it impossible to control the spread of ideas.