Writer-director Sean Mullin’s cross-cultural indie rom-com “Amira & Sam” doesn’t exactly break any new ground. It gets by on low-level sweetness and guile until delivering an unexpectedly powerful emotional sucker-punch at the end. For much of its running time the movie feels like a cheerful if slightly awkward blend of familiar ingredients: A bit of “Green Card” and Tom McCarthy’s 2007 indie hit “The Visitor,” snatches from every bittersweet tale about a war veteran’s homecoming, a few dashes of “Wolf of Wall Street.” Amira (Dina Shihabi), the gorgeous Iraqi refugee of the title, even refers conspicuously to a major point of influence when she attends a party, clad in a spectacular red hijab above a plunging neckline, alongside Sam (Martin Starr), in his U.S.