So I'm an Asian-American female in an engineering grad school, and I think I read/get what OP is saying. I don't judge people's work ethic or intelligence, but language and cultural differences can lead to really huge roadblocks when it comes to working on a team with international students.
This year was my first time ever working with an older, visiting scholar from India, so I recognize my sample size is incredibly small. But this was also the first time that every time I (the only female on the team) brought up an idea in brainstorming or tried to get a word in during discussions, he either immediately dismissed me as wrong, or cut me off completely and did not even realize I was in the middle of speaking. To this end, I imagine it might be a cultural thing, as I've spoken to him about it and tried to do some conflict resolution but he simply didn't think it was a big deal. Is it racist to think that maybe he came from a country that still has a lot of progress to go in terms of feminism and respecting women as equals in the workforce? Maybe, but I kind of lean towards no. Is it racist to assume every male from India would be like that? Yes, and I wouldn't do that. But do I ever see myself applying to a job if I found out a large majority of the workforce were male, Indian immigrants? Based on my experience, no. Is that last part racist? Maybe....? I think this is the sort of "kinda racist" that OP was talking about.
Another thing I can think of in terms of being biased against international students is that if you're working in a group with them, and their English is not up to par, you will be doing double the amount of work because you will have to correct their grammar in every assignment you submit, since they will not know how to do it themselves, and if you don't, your grade will be hurt by it too. Assuming I could pick teammates, and I had two very equally competent options in terms of knowledge and work ethic, but one of them had broken English, is it racist to want to work with the person with perfect English? No. Is it racist to assume that everyone you meet who looks Asian or has an Asian-sounding name on paper will have horrible English? Yes. But if I meet them both, and one of them has great English and one of them doesn't, I'm going to choose the perfect-English teammate, and the majority of the time this will be the white guy/girl. I think this is the sorta-kinda racism that OP has "learned" in grad school.