People from Mexico, Canada, Venezuela, etc. are not Americans.

Is this your unilateral assertion? As an American (a citizen of the United States of), I unilaterally disagree. On the other hand, each of these nations has a unique name which events of a few hundred years ago deprived us. On the third hand, as a Canadian (and, if I recall, a former citizen of the United States), are you saying that you want to be referred to as "an American"?