Some times Iranian students ask me about possibilities of continuing their PhD studies at American universities.
Usually answering such questions are not easy. Studying for a PhD program in any field of engineering at least takes about 42 to 48 months. This is in case that every thing goes smooth and as planned. Some times it may take longer up to 5 or even 6 years due to various reasons. Now considering a single entry visa and need for application for a re-entry visa outside US which there is no any assurance about it, then any Iranian student who plans to apply to American or even Canadian universities should take all of these issues in consideration.
A student even if can get the visa at first stage, he may face any situation that requires his mid-study travel like illness or death of his/her parents or any close relative. Although it was in the news last year that US started granting two entry visa to Iranian students, after a tragic accident which led to death of an Iranian student in Texas when he was in the way for getting his mother at the Houston Airport, however according to some news such visas are counted only for 1/4 of granted visas.
Any way to get a better picture of the situation and in order to have better, well studied decisions it is good to read the following articles: