Aside from the content of the articles, I was interested that this was something L'Express thought would make a good cover story. It was clearly inspired by the DSK affair, where an extremely crude and simplistic summary of the two sides would be that the French cannot believe he actually did it and blame either a conspiracy theory or a prudish American mentality that can't tell the difference between seduction and attempted rape, while the Americans are outraged that the French would question the alleged victim's integrity.
I have a feeling, though, that this is an issue that runs deeper than current political scandal. I've often noticed that the UK press, or at least certain branches of it, shows many more signs of rivalry with the French than the French press with les anglais and assumed that it was an indicator of a British inferiority complex combined with a French sense of superiority to everyone on the planet. Now, however, I think I have come closer to understanding the explanation. The French have much more of a love/hate relationship with the US than with the UK, decrying the damaging effects of the globalisation of US culture while guzzling Big Macs at a rate that is second only to the Americans themselves. So while the British conside the US as an ally and the French as rivals (culturally speaking, at least) the French are far more concerned by the Americans themselves than the nation that they see as their puny "anglo-saxon" sidekicks.