Yes, as someone who has worked at a couple of U.S. journalism outlets, I would say there's a big difference between between the Risen-type of prosecutions and "inspections" by the local officials.

One outright difference is the potential for prior review. James Risen, AFAIK, entered his current legal situation quite a time after the publishing of his story...and this seems to pretty much always be the case with journalism that ends up on in a courtroom. If the NSA had been using its full wiretapping powers to "inspect" Risen, a well known national affairs reporter, then it would've not gotten to the probe stage, or to the publication stage.

Risen of course is facing an intrusive probe, but that is ostensibly part of a post-publication investigation to root out the leakers who are ostensibly breaking laws.

What is happening to Bloomberg, and what purportedly happens to typical Chinese news outlets, is a preventive, chilling action...and while you may argue that the thought of being targeted in a prosecutor's probe can be just as chilling...I'd argue that it's the frequency and the seeming arbitrariness of drop-in inspections is what makes the difference.

And so why doesn't the NSA or even just the local police station doing occasional inspections? Because even if that were legal (which it probably isn't), the public penalty for such actions is so high that most U.S. agencies seem content to duke it out post-publication. I don't know how things are exactly in China, but I think you have to accept that not all intrusions on journalists' work are equal out of principle.

Note: there's obviously selection bias at work here...presumably, we don't hear about the journalism projects that are killed pre-publication, and we only know about the ones like Risen who sneaked their stories through. But I have to seriously doubt there's a significant number of secretly squelched stories, because again, the risk of an agency doing so is that it blows up in their faces, a la Barbara Streisand.