Like the catchiest pop song, American Dreamz can be exuberantly fun, bring a smile to your face, even leave you feeling slightly giddy after it's over.

And it provides zero in terms of actual substance.

Writer-director Paul Weitz's parody of American Idol and America's president is dead-on, filled with perfect details, sharp dialogue and many reasons to laugh out loud.

Dennis Quaid, who starred in Weitz's 2004 corporate comedy In Good Company, is a wholly inspired choice to play the good ol' boy commander in chief, who only understands why the country is at war in Iraq when it's explained to him in terms of comic book characters. And Hugh Grant, the star of Weitz's 2002 grown-up, coming-of-age movie About a Boy, functions beautifully as an amalgamation of Ryan Seacrest, Simon Cowell and American Idol creator Simon Fuller - arrogant and acerbic, but quick-witted and strangely irresistible.

While it's just as timely as those two previous films, American Dreamz lacks the brains of the former and the heart of the latter. It's not that the humour is overbearing; this is by no means a grotesque, over-the-top Saturday Night Live sketch, stretched out to feature-film length. Weitz gets the tone right nearly all the time, and his portrayal of both the presidency and the wildly popular talent competition doesn't feel too far off from the real thing.

But even as the film expertly re-enacts these phenomena, it has absolutely nothing insightful or refreshing to say about them. Wannabe pop stars are ambitious and will say or do anything - even trot out an injured war veteran as part of their back story - to gain sympathy and support from an ever-fickle public. Politicians are managed by an array of handlers who dictate everything they say and do, if only to further their own agendas.

And your point is what? Once Weitz sets up these jokes, it seems he doesn't know where to go with them.

He does start out strong, though, with Grant's Martin Tweed savouring the typically stellar ratings of his TV singing contest, American Dreamz, while breaking up with his latest adoring, blond girlfriend. ("You make me feel like being a better person," he explains. "And I'm not a better person. I'm me.")

The next morning, Quaid's President Staton wakes up after a close election to find he still has a job.

"It was a helluva fight," he says, pointing emphatically with a slice of toast. "The important thing is, the good guys won." (By his side in bed is Marcia Gay Harden, a Texan like the Bushes, doing an eerily accurate impersonation of a Laura-like first lady.)

Their paths ultimately will collide when the president's chief of staff (Willem Dafoe in a bald cap, looking like Dick Cheney but talking like Karl Rove) suggests that he could get a popularity boost by appearing as a guest judge during the finals on American Dreamz.

Among the top contestants are Sally (Mandy Moore, who doesn't get to sing enough), a small-town Midwestern girl with diva-like, big-city aspirations who grudgingly reunites with her ex-boyfriend (Chris Klein) after he's shot in Iraq; and Omer (Sam Golzari), who has left Baghdad to meet up with his sleeper cell in Orange County, and whose love of performing show tunes lands him on American Dreamz completely by accident.

If you faithfully watch Idol (and 30 million viewers do each week, there's no shame in that) you will be thrilled with the attention to detail: the stage, the shameless product placement, the withering criticism. Martin Tweed - "Tweedy," as he's known - describes one singer's performance as "a musical Ebola virus." There's a Bo Bice figure, a Fantasia Barrino figure.

By the time the president gets there, though, he's begun reading the newspaper for the first time in his life and is actually trying to think seriously about what's going in the world. And so when someone shows up with a bomb during the much-anticipated American Dreamz finale, he knows how to handle it. Sort of.

It's all joyfully cynical, if that's possible. And it makes you wish that Weitz, to borrow a phrase from Idol judge Paula Abdul, had taken the material and really made it his own.

Two and a half stars out of four.