For a play running at the Lincoln Center, actors and designers converged on New York from six different countris. “Under most circumstances, obtaining a United States visa is arduous. In the case of these visiting artists, the ordeal involved proving that they had a good reason to enter the United States, that they were not a security threat and that they had no intention of staying in the country. The Trump administration’s travel ban — and the legal turmoil around it — has made the whole process all the more bewildering.”