Dear Student,
The difference between the nation state and the modern state are –
1) Nation states appeared after the downfall of dynasty rule and monarchy in Europe. While modern states, which is governed by a centralised power and authority, took a long time to develop.
2) In a nation state, a common identity of citizens develops as they share customs, traditions and language. While in modern states, people belonging to different cultures, speaking different language and following various traditions live together.
Nation states have evolved into modern states now.
Regards,