The bar at the Willard is too noisy for Harry Shearer, who doesn’t want to talk over the bourbon-swishing belly laughs of happy hour.

Gotta watch the voice. “It’s my meal ticket,” he says, ducking into the mirrored elevator off the gilded lobby.

And, anyway, Shearer doesn’t look like he belongs ensconced in dark-green leather and spit-shined oak, surrounded by navy jackets. The humorist and prodigious voice actor — his meals (and millions) come from Ned Flanders, misters Burns and Smithers, and other characters on “The Simpsons” — sports a Cosby sweater, black corduroy pants, dingy sneakers and a brambly scruff on his bloodhound face. He looks like a college professor lulled into a kind of zen complacency by the anesthetic of tenure: 22 seasons of “The Simpsons,” 28 years of hosting his sociopolitical radio program “Le Show” on KCRW in Los Angeles. He boasts that he can fall asleep anywhere at anytime during anything.

But he will not be falling asleep in Washington. Harry Shearer is in Washington because he’s angry.

Harry, everyone’s angry. Especially at Washington. Take a number.

Yes, he says, but just watch these 97 minutes of footage.

“They just can’t [bleeping] fathom that this was allowed to happen,” he says — “they” being the audiences for his new documentary, “The Big Uneasy” (which will screen Tuesday at the AFI Silver Theatre), and “this” being the post-Katrina flooding of New Orleans, where he lives part time in the French Quarter.

Shearer narrated, directed and financed the film himself. It cost just under $500,000 to produce — not much more than a paycheck from one episode’s work on Fox’s “The Simpsons.”

“I basically funneled some money from Rupert Murdoch,” he quips, settled into an armchair by the window of his hotel suite, looking down on the rush-hour traffic on F Street NW.

“I didn’t formulate the project in my head until the president visited New Orleans in October 2009 and called it a ‘natural disaster’ and said it right to the face of New Orleanians, who were applauding him,” Shearer says. “When I scraped myself off the ceiling I thought, ‘Okay, radio shows and blogging and my Huffington Post articles are clearly are not impinging on either his or his country’s understanding of this event.’ ”

The country’s Katrina complex comes from fixating on human distress, on the people on rooftops, Shearer says. Emotions obscure the truth of the matter: The disaster in New Orleans was caused by an avoidable engineering failure that is being repeated in the rebuilding of the city. “The Big Uneasy” is a movie about plumbing, about underseepage and pounds per square inch, narrated by scientists and whistleblowers.

The villain in his movie? The Army Corps of Engineers. Which comes off as sniveling as Smithers and as brash as Burns.

“If you go around the country and start paying attention to what the corps does in areas where they’ve built levees in other cities, you find a common thread to the way they go about their work,” Shearer says. “You have Sacramento, a river delta city, really in the bull’s-eye right now — the corps said publicly that that system is in big trouble. You have river levees in Dallas that the corps is now acknowledging are built on sand. One of the ingredients in the mix is hubris. Just, ‘We’re the corps, we know what we’re doing.’ There’s no grown-up supervising. There’s no congressional supervision because Congress is so well-served by pork-barrel projects through the corps.”

His voice is a nasal baritone. His manner is mild. The capital-gray office buildings sap the color from the reflected light of the sunset, which washes his craggy face in a cool neutral white. In this setting, at this moment, Harry Shearer doesn’t seem angry.

But he never really is, he says. His comedy is his anger, transubstantiated.

“One of the best-known things I’ve ever been involved in was the men’s synchronized swimming sketch on ‘Saturday Night Live,’ ” Shearer says, “which came out of my outrage that this sport was in the Olympics and they were getting real gold medals for doing that.”

Shearer in the pool with Martin Short.

Shearer the bassist, the novelist, the op-ed columnist.

Shearer trying to get through airport security with a foil-wrapped zucchini in his trousers in “This Is Spinal Tap.”

In college, Shearer majored in political science and later was a low-level staffer in the California legislature for a year. But he ultimately chose the life of an entertainer: more fun than policy advising, but with a license to needle the national discourse through humor.

So, Mr. Civic-Minded Satirist, what do you find most fascinating and most frustrating about the United States?

“I think the most frustrating thing is the almost universal sense in which executives in the media industry look down on their fellow Americans and make choices which reinforce the very stereotypes they delight in having — and we get a populace which is in the dark about a lot of stuff that is done in our name,” he says. “What’s fascinating is the degree to which people in this country can still motivate themselves to collective action. That’s one of the untold stories of New Orleans, post-flood: the huge amount of civic action and civic organizing that came out of that moment.”

He showed “The Big Uneasy” at the GALA Hispanic Theatre over the weekend. On the schedule for Monday: visits to the National Press Club and to the Hill, where he will urge congressmen to decommission the Army Corps of Engineers, then the Tuesday screening at AFI.

Before the Internet, he had one tradition whenever he came to Washington: Go to wherever the Nixon tapes were being archived, put on some headphones and listen to the 37th president warble his way through his psychosis. Shearer loves the guy, and is developing a filmed version of the weirder stretches of the Nixon tapes (starring himself) for British television.

“He’s the ultimate American icon in a way, a totally self-made man who then takes care of the other half and destroys himself,” Shearer says. “I certainly think he set a high bar for conniving and inserting the political into every aspect of the government process, and I think that’s very much with us today.”

Shearer offers a depressing example. Last year he was complaining publicly about the Obama administration’s lack of response to whistleblower allegations and to the Army Corps’s decision to opt for a technically inferior levee reconstruction plan (detailed in the film).

“I will tell you flat-out — without using the man’s name — that somebody who’s arguably quite knowledgeable about Washington said to me, ‘[David] Axelrod and [Rahm] Emanuel don’t want to do anything to help New Orleans,’ ” he says gravely, his voice lowering, about Obama’s senior adviser and former chief of staff. “ ‘That just makes [Louisiana Gov.] Bobby Jindal look good.’ ”

The sun has set. Shadows have overtaken the hotel suite.

“You can’t get more Nixonian than that.”