A soup spoon turns lethal in the unlikely hands of sweet and spacy stoner Mike (Jesse Eisenberg) in the violently paranoid action comedy “American Ultra.” Mike’s a lot like the spoon — harmless unless deployed in the right way — because he used to be a particularly effective “asset” at the CIA, a term used to describe highly trained super-killers. But the program was shut down, Mike’s memories replaced with serious phobias, and he was planted in a sleepy West Virginia town with a girlfriend, Phoebe (Kristen Stewart).