It must be the biggest mass mugging in history. This weekend America is waking up to the fact that a lone British comedian, armed with no more than a false moustache and a chicken in his suitcase, has exposed the superpower as never before.

The perpetrator appears in the hit “movie-film” Borat: Cultural Learnings of America for Make Benefit Glorious Nation of Kazakhstan, which opened in America and Britain on Friday. In fact “opened” is too kind a word: the film, which took nearly $9m in the US in its first night, leading one critic to predict it could break comedy box-office records, has arrived more like a proctologist’s finger up America’s rear in search of its irony gland.

It presents the British comedian Sacha Baron Cohen as Borat, a hapless television reporter from Kazakhstan making a documentary about the “US and A”. It shows him driving across the country mangling the English language and confronting unsuspecting politicians, preachers, feminists and everyday citizens with his sex-mad, mysogynistic, homophobic, anti-semitic, gypsy-bashing views as if these are normal in his country.

“Is it not a problem that the woman have a smaller brain?” asks Borat of a group of feminists. “The government scientist has proved it is size of squirrel.”

When one of the feminists looks appalled, he advises: “Hey pussycat, smile a bit.”

Fans say it’s all designed to mock prejudices in others by revealing what is really under their skin. On the other hand, critics say it’s Jeremy Beadle with a silly accent.

Whatever your view, the film manages to be gross, crude and funny, while flying a couple of jumbo jets into the twin towers of political correctness and cultural sensitivity. It’s also going to make Baron Cohen, who created Borat, a fortune.

British comedy is hitting home in the US on an unprecedented scale. Last week Hollywood handed Baron Cohen £22m to make a film about another of his outrageous characters, Bruno, a gay Austrian fashion fanatic.

Celebtastic wealth, Borat vows, will not change him. “I try to stay normal persons,” he told one US interviewer. “I still shoot dogs. I drink horse urine with the boys. I’m a regular boy but proud of my new status. I am fourth most popular person in Kazakhstan. Number one is children’s favourite animal actor, Joanie the Monkey, the star of many pornos.”

What is changing is British comedy’s international power and reach. Ricky Gervais has reaped a Golden Globe and a cash pile the size of Slough from selling The Office to the US and has lured Robert De Niro to appear in his latest series, Extras.

Eddie Izzard is a big live draw on both coasts of the United States. An American version of Little Britain, which boasts a cast of dodgy gay, disabled and ageist characters, is due next year. And the hot topic in Los Angeles is how to transport Steve Coogan’s character Alan Partridge Stateside.

As these British inventions go west, the frontiers of comedy are shifting, too. After years of being veiled by political correctness, comedians are now finding ways to mullah everyone and everything. Sometimes it wobbles perilously between humour and offence, but audiences for Borat last week were heading for rib fractures, not the exit.

“British comedy is now one of the hottest things in Hollywood,” said Stephen Armstrong, the Sunday Times critic and Edinburgh Festival comedy judge. “The staggering wealth pouring in is something that has never happened before to British comedy.”

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