> does this line of reasoning apply to the US only, or in general?

Are you asking serious questions? I think the evidence shows the U.S. was negotiating in good faith in the beginning (and I'm scoping to this round of negotiations only). And then it concluded there was no deal to be had, and we probably started bullshitting as well. At the same time, I think the evidence shows the Iranian side was mostly bullshitting the whole time.

> they had an option to do it and still continue a diplomatic track

Well sure. We also had the option to terminate negotiations, ratchet up sanctions and walk away. None of that changes that the Iranians weren't negotiating in good faith. (Again, based on what I've seen. Open to changing my mind. But the lack of any discussion of what Iran did in this subthread seems to underline my point.)

> they aren't obliged to devote themselves to the US preferences at the US-preferred pace

War is politics by other means. They aren't obligated to accept the other's timeline. But I wouldn't say that's negotiating either realistically or in good faith–you can't just ignore material variables because you don't like that they exist.