Four Indian students were rejected for U.S. visas after undergoing a new Trump-era social media screening. All were told they had failed to prove ties to India. Kaushik Raj felt like his future was falling into place. He’d just won a $100,000 scholarship to pursue a graduate degree in journalism at Columbia University. A U.S. visa was the only thing that stood between him and a new life in New York. Raj, 27, wasn’t overly concerned. He had completed every stage of the traditional application process. As a last step, he had to allow American authorities to vet his “online...