If States severed diplomatic relations with another State ... How this affects the other State?

Question

If States severed diplomatic relations with another State ... How this affects the other State?

Answer 1

I assume you mean, if one of the United States severed relations with another of the United States, e.g. if Texas severed relations with Louisiana... if that's the question, the answer is simple: It can't happen. That would be the equivalent of secession, which would be a prelude to civil war, and the Federal Government would ultimately use the Armed Forces to take over that state and have its local government replaced.

If you're talking about the former Soviet Union... well, you'd need to rephrase the question. ;)