Barrington 1997 (227 cites), the first result when you search "definition nation" in Google Scholar, defines a nation as "a collective united by shared cultural features and the belief in the right to territorial self-determination." The United States certainly falls into this definition.
This is almost identical to the use Bret Devereaux uses in the artice.
It is not any shared cultural feature (but e.g. a common origin myth would fit), and the people have to feel a sense of purpose, of common past and future relative to their homeland. As stated in the article, that certainly fits Native American Nations, but not the US as a whole, as Barrington discusses in the next paragraph, "Nation: Misuses".
From Barrington: "Also, and more important, nations need not even be based on a certain ethnic identity. Thus, the words "shared cultural features" in the definition of nation above should not be read as "shared ethnic identity."
Very few European nation states fit Devereaux's concept of a nation. The Normans (Scandinavian), the Franks (Germanic), and the Galic-Romans (Romanized Celts) all make up a significant part of the historical French population. And yet, even though a majority of French citizens didn't even speak French until the 19th century (compare this against a 75-80% English literacy rate in the US at the same time), no one today would argue that France isn't a nation state.