Well, they may have been born here but they didn't accept America and didn't become true Americans. Who would use their left hand to cover their heart?
They are placing their left hands over their hearts. It's not a pic someone reversed because you can see the wedding rings on their fingers. The Obama's are NOT American!
The least bit of research in google, which you are incapable of, apparently, reveals that this pic is a fake. Even so, it turns out that the left hand is appropriate in certain circumstances (I did not know that).