For CNN, another international crisis means another opportunity — until, of course, it doesn’t.

Turmoil in the Middle East and a devastating earthquake in Japan have once again ratcheted up U.S. interest in what’s happening overseas, triggering a related flurry of stories about how CNN has been the beneficiary. Once again, CNN is talking about how to parlay its temporary ratings surge into renewed vigor and an improved competitive standing.

If that sounds familiar, it should. Top CNN execs probably don’t want to hear that they sound like Jonathan Klein, but in early 2005 their predecessor at the channel was saying a lot of the same things after ratings spiked in response to the Indonesian tsunami. “CNN Demonstrates Global Strength With Tsunami Coverage,” read one press release at the time.

Yet CNN’s strength has also consistently turned out to be its glass jaw — a function not merely of missteps by the channel (though there have certainly been plenty of those), but a short U.S. attention span when it comes to sustaining focus on crises abroad.

In November, CNN put out another press release touting how over the course of a month, the third-place cable news network — behind Fox News Channel and MSNBC — actually reached far more people overall than either of its competitors: 95 million tuned to CNN, per Nielsen data, compared with 83 million and 79 million for Fox and MSNBC, respectively.

Those numbers have long demonstrated the radio-like dilemma CNN faces: Its cumulative audience, or “cume,” is generally higher, in much the way more motorists listen to news radio — for traffic, weather, scores — a few minutes at a time. But its average audience at any given moment is significantly lower, due to lengthier tune-in for Fox and MSNBC’s opinion hosts, where the format approximates talkradio.

Normally, in other words, making claims about wider reach isn’t good for much. Ratings are sold based on who saw the commercials, not who dropped by during the week.

What reach does mean, though, is when people seek out cable news in heightened numbers, CNN often serves as their default setting. Even with cellphone video and feeds from international partners, rivals can’t match its web of international correspondents — and MSNBC, reluctant to break away for news even out of canned prison documentaries, appears to have little interest in trying.

For CNN, however, the vagaries of news cycles have always made the channel vulnerable, which explains its attempt to re-program primetime with studio-based hosts. Even if they’re not breathing fire out their nostrils like Sean Hannity or throwing darts like Rachel Maddow, the idea relies on viewers showing up because they like the style and delivery of Piers Morgan or Anderson Cooper, not necessarily because they’re driven by the news of the day.

Although developments in the Middle East remain a work in progress, there’s scant reason to believe Americans will consistently follow what transpires there. And initial sympathy for the Japanese people quickly graduated to more insular concerns — like whether that radiation leaking into the atmosphere could potentially reach the U.S. West Coast.

Throw in the seemingly interminable campaign season, and CNN will likely find itself back at square one relatively soon — torn between the better angels in its journalistic nature and Morgan’s clear willingness to pander with the latest Charlie Sheen news, which threatens to become to his show what O.J. Simpson was to the fellow he replaced.

A steadfast commitment to hard news — even more so than being politically nonpartisan or “aggressively independent,” the term CNN/U.S. exec VP Ken Jautz used in describing the net to the Associated Press — would establish CNN as a clear alternative. Yet that will also require enduring the ups and downs of a media landscape where fluff and celebrity are not only cheaper to cover but also more attractive to casual news viewers — just like the ones who, in a crisis, periodically stop by CNN.

In a way, CNN’s current situation brings to mind the slogan CBS coined for use in connection with its Olympic coverage: “Share a moment with the world.”

Of course, that omits a secondary thought that isn’t quite so favorable to the channel: “And then get back to covering the latest on Charlie Sheen and Chris Brown.”