This time Sacha Baron Cohen ambushed all of us. His new Showtime series, “Who Is America?” — his first television show since “Da Ali G Show” went off the air in 2004 — was announced just last week and makes its debut on Sunday night, riding a short but intense wave of hype.

Carrying out Mr. Cohen’s elaborate deceptions and gathering enough successful ones to make a seven-episode series takes time, though — Showtime said “Who Is America?” has been “in the works” for a year. And that may have something to do with why the premiere episode feels tepid and inconsequential. During that year, we’ve gotten so used to people saying crazy and hurtful things of their own free will in public that watching them being tricked into doing so doesn’t have the entertainment value it used to.

[Mr. Cohen has been duping politicians for decades. Here are his greatest hits.]

To be fair, while Mr. Cohen’s methods remain largely the same, his new show is framed differently, with less of an obvious emphasis on maneuvering high-profile victims into gotcha moments. (A segment with Sarah Palin, already well publicized, is not in the first episode, the only one Showtime provided to critics.) An introductory montage announces that “four unique voices will reveal who is America,” and while the echo of a news documentary unit is certainly meant to be parodic, “Who Is America?” doesn’t always transcend the association. In place of the rough, anarchic glee of “Ali G” and Mr. Cohen’s masterpiece, the feature film “Borat,” the humor in the new show has more of the studied, calculated texture common to the news-inflected late-night shows that have taken over topical comedy in his absence.