US politics is overshadowed by bitter debates over sexual politics, from abortion to contraception and personal morality. But it is not just rightwingers who fear the increasing sexualisation of society

Dr Marty Klein pulled no punches when it came to what he thought of the ferocious debate in America over contraception. As the nation's political classes veer between condemning government funding for birth control and defending it as a basic women's right, the California sex therapist and author of America's War on Sex bluntly said his country was on a perilous path.

"America has entered a new dark age where people are proud of their ignorance," he told the Observer. "The US is careering towards a society that is reshaping women's reproductive rights. It used to be abortion. Now it's contraception. How can contraception be a battleground? It is crazy."

That might be so, but the spat is white hot and part of a much larger argument. Only last week protests broke out in Texas, Arizona, Utah, Georgia and Alabama that all involved some aspects of sex and sexuality. In Utah, it was over the passing of a law that means the only sex education children will get in school will be about abstinence. In Texas, it was about cuts to health insurance that covers birth control. In Georgia, eight of the nine women in the state senate walked out over a bill that attacked abortion rights.

Barely a day has gone by in recent weeks without some fresh fight breaking out over sexual politics. The most fierce was over radio shock jock Rush Limbaugh's comments on Georgetown University law student Sandra Fluke, who had testified in Congress on the importance of government mandated funding for birth control. Limbaugh told millions of conservative listeners that this made Fluke a "slut" and "prostitute".

He said: "If we are going to pay for your contraceptives and thus pay for you to have sex, we want something. We want you to post the videos online so we can all watch." The comments sparked outrage, triggered an advertiser boycott of Limbaugh's show and dragged in all the Republican nomination candidates and Barack Obama.

Limbaugh apologised, but many liberals saw it as a sign of the powerful forces on the right determined to undo decades of advancement in sex and women's rights. Few people symbolise that more than former Pennsylvania senator Rick Santorum, who is now the main challenger to Mitt Romney for the Republican presidential nomination.

A devout Catholic and hardened culture warrior, Santorum is a hero to conservatives for his hardline views on abortion and contraception. For Nancy Cohen, author of the current hit book Delirium: How the Sexual Counter-Revolution is Polarising America, Santorum's rise is the inevitable result of decades of backlash against 1960s sexual liberation. "It is insanity to be having this conversation in our politics when you are a world power. The rest of the world is watching with their jaws agape," she said.

But the image of America gripped by a fervent new puritanism is not the full picture. Any survey of the wider cultural landscape reveals sex has never been more prevalent in American life. On television and in movies sex is everywhere.

Reality shows like The Jersey Shore show their cast members coupling with each other and random strangers. Stars such as Paris Hilton and Kim Kardashian, built lucrative businesses on the back of sex tapes. Gossip websites debate the sex lives of celebrities with a prurient detail that would shock even the most infamous of scandal rags from Hollywood in the 1930s, and they do it for an audience online of millions.

Sex sells like never before, even for the most tangential of products. In sport there is even a Lingerie Football League, whose female players done skimpy outfits and teams have names like the Los Angeles Temptation.

The American sex industry is said to be worth more than $12bn a year. Recent regulations in California aimed at ensuring all porn actors have to use condoms saw protests that such a law would see the industry relocate, with a resultant loss of jobs and taxes. At the same time porn actor James Deen has been cast as the lead in a new Hollywood film The Canyons. Deen has now become such a popular porn star – especially with young women – that he was the subject of a segment on ABC's headline news show Nightline.

In fact, sexual freedom in America has gone so far that conservatives are not the only ones wringing their hands. The sexualisation of young girls – such as Bratz dolls with their bee-stung lips and short skirts – has outraged liberals and feminists, as has the growth of a casual "hook up" culture on American college campuses. Even Klein admits that – sexually speaking – Americans have never been so inventive. "The range of things that people do in their bedrooms is without doubt getting broader and the entertainment options around sex are also broader," he said. But how to explain such vibrant sexual freedoms alongside such a widespread backlash? "Two words: mental illness!" joked Klein. "When people ask me is America getting more progressive sexually or is it getting more conservative, I just answer: 'Yes'."

Cohen has a thesis. In her book she describes a "shadow movement" that has aggressively campaigned to set back women's rights, focused on issues around sex and birth control. It is, she says, largely motivated by religion. That gives it a powerful motivation and it has developed sophisticated techniques to influence mainstream politics, especially via the social-conservative wing of the Republican party. Klein believes it gives the movement power far beyond its numbers and a louder voice than a more silent majority. "These people are brilliant political organisers. They are ideologues and crusaders. They believe if they lose, civilisation hangs in the balance," he said.

Unique factors in American history also help to explain the situation. Religion continues to play a big role in public life, which stands in stark contrast to many European countries. About 43% of Americans regularly go to church and it is hard to have a political career in the US without professing a deep faith. The power of religion provides a ready-made vehicle for campaigning on sexual mores. It also means sex is the one part of life where the normal rules of the free market are given a willful pass. "The only place in life in America where more freedom of choice is seen as bad is sex," said Klein.

Many commentators say the hardline Protestantism of 17th-century settlers casts a long shadow over modern sexuality, leading to a distrust of sexual behaviour as pleasure and seeing it as a religious duty for reproduction. Certainly Santorum's pronouncements on the evil of contraception fit this narrative. Despite his Catholicism, Santorum is a huge hit with the evangelicals. But others say the Puritans have been misjudged by history.

"There is evidence they understood and celebrated sex within certain confines, like marriage," said Professor Thomas Foster, a cultural history expert at the Catholic DePaul University in Chicago. "Puritans talk about the clitoris. My classes are always amazed when they hear about that," he added.

Another theory is that American ideas about public and private morality are rooted in the nations' founding fathers. Whereas in France and Italy, there is little link seen between a politician's private life and political behaviour, in America the reverse is true. "There was a sense with the founding fathers that the person who is virtuous in their private life is able to be virtuous in their public life," Foster said. Thus Bill Clinton's affair with a White House intern nearly destroyed his presidency.

A final theory holds that, because America was founded as a revolutionary experiment against the autocracies of Europe, it has a very different sense of "modernism". While European countries have organically evolved social mores over centuries, America has always been in turmoil at the previous generation's social behaviour because such fights are locked into the nation's sense of self-invention. In this view, the current battle over contraception is simply yet another part of the American experience.

"These debates are old. They are as old as the first colonies," said Foster. Or to put it another way, the only thing more American than having sex is arguing about it.

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