Any geographical boundary change in territory of any country will trigger the change in policy of regional countries, its very obvious, what's really confusing you?Kashmir is merely a flash point of hostilities between two religious communities. It's unproductive to view it as an insulated territorial conflict. Yes, Southern states are less likely to have strong opinions on Kashmir but you deal with India as a whole through the central government which represents all states. So when you point nuclear weapons at India, it includes the North, South and East. It's similar to how the rest of the world deals with the EU.