Why is getting your PhD in Iran invalid for obtaining a post-doc position in the US?
I think the answer is simple: your premise is false. There are no rules/regulations forbidding an Iranian earned PhD from being a postdoc in the US.
It might be hard to get a postdoc in the US for anyone whose academic background, and PhD earning institution, is not perceived as highly ranked.
Note: I have answered this a year and a half ago. Things may have changed since then through the presidential ban against Iranians entering the US. I have no specific knowledge of the current situation with respect to Iranian students.
As with the other people answering this question, I don't think your friend's problem is that her PhD is "invalid". I've worked with a number of Iranian researchers and graduate students, and it's never been brought up that Iranian PhDs are looked at as any way "lesser" or invalid compared to any other degree.
Which leaves one of two possibilities:
- Her PhD is invalid, not because she is Iranian, but because of some element of the PhD itself, her institution, etc. Without knowing more, of course, we can't really come up with a reason why this is. There are some American PhDs which are invalid, but that doesn't imply that they all are.
- Regardless of how well respected her degree is, an Iranian student may still fall in the "More trouble than they are worth" pile, either due to immigration issues, perceived political instability ("Every time you go home for break, there's a risk you won't be able to get back), or funding issues. This isn't universally true for all universities, but may be true for a particular admissions/hiring committee.
I am going to differ from Dilworth's answer a little bit. While I would not say that a degree from Iran is invalid for study in the US, being an Iranian citizen in the current political climate of 2016 poses some significant hurdles for study in many other countries around the world. Applicants from Iran face heightened scrutiny and substantial delays when applying for visas; in some disciplines, such as nuclear engineering, it may be even impossible. Moreover, the process will very iikely impose additional paperwork and other bureaucratic burdens on the hiring faculty member and institutions. Consequently, many faculty choose to deal with these obstacles by simply excluding all Iranian candidates from consideration.