If one uses the term "American" to mean "a citizen of the United States" then to me it seems self-evident that people from other countries are usually not Americans. Of course Mexicans who come here legally and become naturalized citizens are American (meaning a citizen of the U.S.), as are people of Mexican ancestry who are born here.
As for the rest of your post, two comments: 1) I believe you are much too quick to assign me to a "side" on this thread. I don't disagree with everything you've said on this thread and I don't agree with everything said by the the other posters I pinged. I just thought you were missing the boat on this particular aspect of the debate, that's all. 2) Way too many insults in your post. Yes, this subject does bring out some racist comments at times, but I believe that's not the great majority of posters here.
John, the very definition you posted contradicts this statement of yours. What gives?