He is NOT Mexican. Look at the law and the records. His father, George Romney, was born in Mexico to two US citizens, therefore, by law, he is an American citizen. Because he was a citizen, Mitt Romney, being born in the US with two US citizens as parents, he is by law a Natural Born Citizen.
The Constitution is the law of the land and those that say it doesn't matter are either fools, liars, or Obama shills with their collective nose so far up his butt that they are suffering brain damage due to lack of air. It is important that the Constitutional Law be upheld at all costs, failure will only create destruction. Those claiming that the US President is responsible for the entire world should think that maybe the President should take care of the US interests first, then worry about what the rest of the world thinks.