United States is extremely dependent on the research done by the international graduate students, especially in the field of Engineering and medicine. I am not aware of any Engineering research institute in the US that has no international students. Yet, those intellectuals are treated like terrorist when it comes to crossing the borders. It doesn’t matter how many semesters these graduate students taught American undergraduates or how many papers they published. All their achievements are demolished as soon as they cross the border. I know for a fact that some international graduate students were not allowed to come back to the State after they went back home to visit their families. In some cases, those are PhD students who have only one year to defend their thesis, alas! For this reason many international students decide not to cross the border until they get their degree. This act causes international students to feel resentment about their situation and how they are treated as undervalued person despite their hard work and sleepless hours.
phdcomics.com explains another scenario where international students can’t go to an international conference, even if they are the first author, because their American visa is expired and they need to renew it when they come back to the US, a place where they have been doing excellent research for more than five years!