Why does Mitt Romney, or any other candidate, need to give a major speech to say that they will govern as an American and not let their religion be an issue? We can answer that with another question: Why do so many Americans think it necessary for any and all candidates to believe in God, and more specifically, Jesus Christ?
The most problematic portion of the speech, for me, was this: "Freedom requires religion, just as religion requires freedom" and "Americans acknowledge that liberty is a gift of God, not an indulgence of government." I see liberty as being a gift from the founding fathers, and everyone else who put their necks on the line--literally--to gain independence from England. It's also a gift from every single one of the military people who leave their families, for months, and even more than a year at a time, to protect all Americans and our way of life. I'm pretty sure they don't sort us out by religion as to who is more deserving of that protection. Nor are all military personnel Christian.
But what about those who do not accept Jesus Christ as their personal savior? I would never vote for or against a candidate based solely on religion. I want to know what s/he is going to do about the economy; how to handle the Iraqi problem in a decent and moral way; how to get math and science scores back up so Americans can be more competitive in the global marketplace; how to bring more jobs back in the US; how to handle the environmental crisis; as well as a few other issues I can't think of at the moment.
Basically, I don't care if a candidate is Christian, Jewish, Muslim, Mormon or any other religion--nor do I care if a candidate is agnostic or atheist. What matters is not who they worship, or if they worship, what matters is how they will govern and whether religious beliefs will influence how they govern. It is a very sad state when candidates for elected office feel that is has become such an important issue that they ask reporters follow them to Sunday (or Saturday) services.
We've spent seven years with a president who wears his religion on his sleeve, to the point of having evolutionary science demoted to a "theory," abstinence only programs promoted both here and abroad, the Supreme Court packed with ideologues, though what we were ostensibly looking for was judges who would not legislate from the bench. Because that's a bad thing--but only if you're a Democrat.