[@Willy Vereb]

Prussia already has significant catholic populations. They're not the majority, but they are there.

Kulturkampf also being a product of Bismarck is:
1) in the future, beyond the scope of the RP, it's like worrying about the Franco-Prussian War right now.
2) a product of Bismarck, who being a Protestant Junker, may or may not exist or have the influence of his class in Prussian society.