What, Mexican flag and not an American flag?????

So what's up with this. I thought I was in Mexico for a minute then I slapped myself and looked around me. So it has always been a belief of mine that if you come to America alias United States to live from another country that you become a citizen, you know like you are an American now, not a Mexican. So that would mean that you should be flying an American flag not a Mexican flag. Hummmmmmmmm, should you want to check it out for yourself if it is still up it is at 1380 S Main Street in good old South Salt Lake City.