A message seeking comment was sent to the Department of Homeland Security.
Hameem Shah, a resident of Plano, Texas, said he was returning in 2019 from a vacation to Serbia and Bosnia when he was pulled aside at the Los Angeles airport for additional screening.
There, officers separated him from other travellers and started reading his personal journal despite his protests and asked him whether he had travelled in the Middle East, saying they wanted to make sure he was a "safe person," the lawsuit said.
They asked him about his religious beliefs and practices and searched his phone despite his opposition and released him two hours later, the suit said.
"I thought that being an American meant that I and others are free to practice any religion that we choose," Shah said in a statement on Thursday. He said the experience still haunts him.