I've often heard it said that the Treaty of Westphalia was the origin of the modern nation state, and yet I don't actually know what that means.
What practically changed as a result of the Treaty?
Or if you prefer a though experiment, If there had been no Treaty of Westphalia, what practically would be different in say the "Holy America Empire" with it's "50 principalities"?
Interpretation of the Treaty and its significance varies radically depending on whether you are an historian or a political scientist. There is always more to be said, but we've discussed the key differences in several earlier threads which you might like to review while you wait for fresh responses to your query:
Why is the Treaty of Westphalia significant?, with me, u/mikedash
What ideas did "Westphalian sovereignty" replace?, with u/sunagainstgold
If the Peace of Westphalia established a new way of doing business between European states, what was it replacing? with /u/Aeoleth