Jordan Peele’s “Us” begins so spectacularly well, and sustains its game of doubles so cleverly for most of its two hours, it’s an unusual sort of letdown when the story doesn’t quite hang together and “deliver” the way Peele managed with his 2017 debut feature, “Get Out.” That movie sent people out of the theater with rattled nerves and a pleasurably uneasy catharsis; the new film’s culminating scenes are roughly equal parts “wow!” and “wow?” And that shouldn’t deter you in the slightest.