So in my Early Modern Europe class my teacher mentioned the idea of confessionalization and how it helped act as one of the building blocks for the modern state. The idea sounded very interesting but she did not go into much detail. Hopefully someone can give me a more in depth explanation!
You may be interested in reading prior posts on the Treaty of Westphalia, which closed religious war known as the Thirty Years' War.
The way that the Peace of Westphalia was negotiated was very important, and it's a missed opportunity that your early modern europe instructor did not go into any detail!