For the article on the pope, Clarin seems to have used estadounidense, norteamericano and americano to refer to things and people from the US, though americano in reference to "imperialismo americano." Well, I'm assuming that's the US given the mention of the CIA, but perhaps they are referring to some sort of pan-continental imperialism I'm unaware of.
La Nacion uses americano, but has to specify "continente americano" as if simply saying "americano" wouldn't be clear to readers. They otherwise also use estadounidense and norteamericano.
Neither appears to ever use "americano" by itself to refer to people from the continent, but if you're telling me that if you walked up to someone on the street and said you were an American and they would interpret that as you from the continente americano, then I believe you.
I'm still going to use the demonym American for myself (as everyone gets to pick their own demonym in their own language) and use it to refer to people from the US, but if you to call you an American, who am I to say no? You can call yourself an American, I can call myself an American and everyone is happy.