How did religious pluralism challenge the concept of a unified Europe?

Just guessing but the Latin Countries (France Spain Italy Portugal) remained loyal to the Roman Catholics and Germany, the low lands and England rebelled against it

Hmm I am not sure actually

In a true democracy religion should be separate and therefore irrelevant. However the people involved often hold religious views and sometimes don't have the discipline to prevent those views from interfering with their political decisions, so that complicates things. It's a work in progress.  

Do your own homework