North Korea returned Otto Warmbier, 22, to the US last week, saying he had been in a coma for a year and that it was acting on humanitarian grounds.
His parents said he had been subjected to "awful torturous mistreatment".
Mr Warmbier, who was jailed for trying to steal a propaganda sign from a hotel, did not regain consciousness.
Mr Trump said that a "lot of bad things happened" to Mr Warmbier, but added: "At least we got him home to be with his parents, where they were so happy to see him, even though he was in very tough condition."