The word American, as both an adjective and a demonym, can be tricky. The word technically should apply to people and things both North and South American, but in practical usage it has come to refer mostly to people and things from the U.S.
American as a demonym
The United States has been accused of appropriating the term American out of conceitedness, but the issue is not so simple. Most countries in North and South America have obvious demonyms—for example, Canadian, Mexican, Honduran, Brazilian, Chilean—but for natives of the United States there is no obvious equivalent that rolls off the tongue. United Statesian doesn’t work. So while the appropriation might be unfair to other people of the Western Hemisphere, it’s also a matter of convenience.
Although the use of American to describe U.S. natives may seem illogical, it is widespread and well-established and probably isn’t going to change. These non-U.S. news outlets seem to have no qualms about using it:
An American who sold his construction business and travelled to Haiti to help earthquake victims has been arrested over allegations that he kidnapped an infant. [Guardian]
The people who need to get paranoid are those U.S. diplomats who failed to realize that an American was stoking the anti-Americanism of The Border. [The Globe and Mail]
These are just two examples among many.
Where many people who care about these things draw the line is in the use of America instead of the United States in naming the country, as in this example:
Former US President Jimmy Carter says America is ready to elect a gay president. [The Economic Times]
But this is going to happen whether we like it or not.
American as an adjective
Usage authorities differ on whether it is acceptable use American as an adjective. But, again, it happens, and there’s nothing we can do about it. These non-U.S. news outlets, at least, don’t seem to mind using American as an adjective:
Omar Khadr has fired his American lawyers less than a week before his military commission pre-trial hearings are slated to resume in Guantanamo Bay. [CBC]
The roof of an American football stadium in Minneapolis has collapsed after a blizzard dumped thigh-deep snow on some areas of the upper midwest of the United States yesterday. [Sydney Morning Herald]
Again, these are just two examples among countless ones.
We like to use U.S. instead of American as the adjective, and we’re not alone in this:
The new U.S. goods subject to tariffs also include grapefruit, pistachios, chewing gum, cheese and ketchup. [Bloomberg]
Berkeley’s City Council decided Tuesday night to put off a vote to honor a U.S. soldier who’s accused of sharing secret military data with WikiLeaks. [San Francisco Chronicle]