Take the attack itself. What does it accomplish to deface an American's newspaper's website?
The article doesn't say anything about defacement, it actually says that journalists themselves were the targets. I assume being able to penetrate a journalist's work account is one of the first steps to either subsequently penetrating that journalist's personal accounts elsewhere, or to build a profile in order to create false identity elsewhere. The first could be used to reveal current sources, and the latter could be used to ensnare future sources.
Everyone is on high alert to stopping their own Snowden event, and I think that's a far simpler and more relevant explanation than "USA is trying to frame other countries by defacing its own news site"