how did the treaty of westphalia change the modern state?

Answer 1

I don't think it changed, so much as it established

1. The principle of the sovereignty of states and the fundamental right of political self determination
2. The principle of (legal) equality between states
3. The principle of non-intervention of one state in the internal affairs of another state

It directly recognized the individual right of states to determine their religion, and that Christians not of the state supported sect had the right to practice their own sect.