There are few universally sacred cows in American politics these days, but the families of the victims of 9/11 are among them – conservative pundits Ann Coulter and Glenn Beck notwithstanding.

So with the bombshell that News of the World reporters may have sought not only to hack into their cell phone records and voice mails but to bribe a former NYPD officer to help, the US government finally got engaged in doing more than posturing.

Of course, a fair bit of posturing – some of it deserved – was clearly going to be the end result of the News Corp scandal here, even if the scandal itself remained confined to British soil. After all, News Corp is the parent company of the politically-divisive Fox News, and any whiff of scandal was going to be red meat for an exhausted and increasingly demoralised Democratic base in need of something else to think about.

And from early adopters Senator Jay Rockefeller (Democrat, West Virginia) to Senator Frank Lautenberg (Democrat, New Jersey) to the plethora of House Democrats who joined in the chorus to investigate News Corp for hacking Americans, violating the Foreign Corrupt Practices Act (which prohibits the payment of bribes abroad by any company with any American operations) and for possiblly violating the accounting rules of the Securities and Exchange Commission (by paying bribes abroad and covering them up), it was clear that the interest had far more to do with News Corp. (and its subsidiary Fox News) than any real interest in the virtually unknown-to-Americans News of the World.

There it might have stayed, what with some Republican Congress members like Congresswoman Mary Bono Mack (Republican, California) initially satisfied with NewsCorps assurances that the problems were confined abroad. That is until the 9/11 Parents and Families of Firefighters & World Trade Center Victims came out in favor of an investigation into whether they were hacked. With that, House homeland security chairman Peter King (Republican, New York) proved himself far less likely to rely on News Corp's statements alone and called for an investigation, given his constituents' close connections to 9/11 and his own reputation as their biggest defender in Congress.

King, a frequent guest on Fox News programs whose hearings on Muslim radicalisation earlier this year garnered him more than a fair share of criticism on every other network, was apparently the last crack in the proverbial dam at the Department of Justice, which announced only a day later that they were beginning a probe into whether News Corp. employees attempted to hack 9/11 victims' phones or records.

The investigation, of course, will be just more ammunition for those who hardly need an excuse to bash Fox News, especially after some of its talent made their names questioning the patriotism of various liberal political figures (including President Obama).

Any proof that News Corp did try out its phone hacking here could jeopardise more than an as-yet incomplete acquisition or one newspaper. As the LA Times noted, convictions among News Corp employees could potentially endanger the company's broadcast licences in the US and, as King's call for an FBI showed, endanger the company's reputation among once-loyal conservatives. That would likely be a bigger loss to the company than even News of the World, given Fox News' near-monopoly on conservative viewers these days.

• This article was amended on 15 July 2011. It originally referred to Mary Bono Mack as a Florida congresswoman. In fact she she represents California's 45th congressional district. This has now been corrected