Hassan Kamal Wattoo, 25, had received threatening calls for months from Pakistani authorities angry about critical articles he wrote. When he earned a scholarship to study law at the University of California, Berkeley, he jumped at the opportunity to leave Pakistan, and thought he might work in the US after that.

Then came the detentions in the US of non-citizen students for participating in pro-Palestinian protests, the arrest of a woman who had criticised Israel’s war in Gaza, the cancellations of hundreds of student visas with little or no explanation and what many have described as an assault by the Trump administration on science and academia.

Now, Wattoo said, he plans to return to Pakistan next week, after he receives his degree. His parents, worried about being harassed at the border, decided against travelling to Berkeley to attend his graduation on Friday, he said.

“That respect in the American system has kind of faded away and been replaced with this bitter animosity,” Wattoo said. He described the Trump administration’s tactics as “shockingly similar to what I’ve seen all my life and what I wanted to run away from”.

The New York Times asked international students at US colleges and universities to share how the administration’s immigration policies had affected them, and 150 readers responded. The Times interviewed 20 of them, many from countries where the State Department has said that free speech is restricted.

Some said they had cancelled spring break or summer travel plans over fears that they might not be allowed back into the US. Others said they now avoid speaking in public about divisive issues or participating in protests that they think could attract the attention of the authorities, such as those in support of Palestinians, labor rights or disability rights.

Many said that they had deleted social media profiles or unfollowed accounts belonging to activists. And several said they had applied to transfer to universities in Canada or Europe or were considering it.

Of course, there are about 1.1 million international students in the US, and those interviewed by The Times do not necessarily reflect a representative sample.

Nearly all of them said they were committed to staying to complete their degrees. Still, most of those The Times spoke to made clear that, for them, the idea of America as a pillar of free expression and intellectual openness had faded.

Anton Dolmatov, a Ph.D. student at Rice University in Texas, said that it was jarring to see echoes of the fears he had grown up around in Russia emerge in the US.

As soon as Trump was elected in November, Dolmatov, 28, said, he started applying to transfer to schools in Britain because of concerns about what could happen to his student visa.

He cancelled plans to meet his parents in Turkey and a trip to a conference in London because he was concerned about not being allowed back into the US.

“Just think: essentially to escape Russia, to find oneself in a situation where you also have to be concerned about lawlessness and not having your rights respected, for there not to be due process and arbitrary arrests,” Dolmatov said. “I wouldn’t believe it would happen if I was told it 10 years ago.”

He said he had been accepted by three universities in Britain but was waiting to hear how much research funding they could offer.

International students said recent detentions had stoked doubts about whether they could depend on constitutional free speech protections.

In March, Mahmoud Khalil, a leader of pro-Palestinian demonstrations at Columbia University, was detained by federal agents and remains in custody in Louisiana. The same month, Rumeysa Ozturk, a Tufts University student who had written an article criticising Israel’s military offensive in Gaza, was handcuffed by federal agents in plain clothes in front of her apartment building and held for six weeks.

One graduate student from Lebanon said that when she first arrived on her campus in Florida last year, she felt freer to speak out than she had in her home country, where she had received threats for criticising Hezbollah, the Iran-backed militia.

But since Trump took office, she said, she no longer feels comfortable publicly discussing potentially sensitive issues.

“It’s made me feel stuck in a way, constantly stressed and unsure about what’s safe to say or do,” said the student, 23, who like others interviewed for this story requested anonymity because she feared being deported.

A recent graduate who earned a film degree from a university in the western US said the current climate reminded him of his home country, Singapore, where protests are illegal unless pre-approved by the authorities.

In recent weeks, he said, he avoided walking past two anti-Trump protests on campus for fear of even being photographed near them. The biggest draw of studying in the US, for him, had been the freedom it offered to learn about making films without self-censoring. He no longer feels he can do that and is considering returning to Singapore, he said.

Changes implemented by the Trump administration have resulted in the cancellation of more than 1,800 visas for students at 238 universities as of May 12, according to an analysis by The Times. The administration reinstated more than 1,100 of the visas but has said it is working on a new system, which could result in some international students losing their legal status again.

In response to questions from The Times about its crackdown on student visas, a White House spokeswoman, Anna Kelly, said that it was a privilege, not a right, to study in the US.

Apparently referring to students who had been penalised for participating in pro-Palestinian protests, Kelly said that secretary of state Marco Rubio “has the right to revoke visas for non-citizens pushing the propaganda of Hamas terrorists who have held Americans hostage”.

Despite the uncertainty over visas, many students said they still wanted to get jobs in America after graduation, and that they valued the diversity of US campuses and the economic opportunities the country offered.

Students who travel far from home in hopes of improving their career prospects and having a positive impact on the world “should be prepared to take on this risk, and that’s something I decided well before I even came here”, said Ryan Li, an 18-year-old Canadian studying at Georgetown University. He was not going to let the shifting political climate dissuade him from studying in the US, he said.

Carlos Noyola, a Mexican student at the University of Notre Dame, said he had begun to feel unwelcome, which he hadn’t experienced in his first three years in the US.

On a recent weekend, a bouncer at a bar in Chicago told Noyola that Trump was going to deport him.

The administration’s policies are affecting him in other ways, too: With universities offering fewer research positions because of federal funding cuts, he is applying to universities in other countries.

He had grown up with the perception that the US was a superpower, “not only in economic and military terms, but also in intellectual terms”, said Noyola, 28.

“I don’t want to say that it’s over now. Hopefully it’s not.”