The courts have already spoken on this issue. The aquisition of foreign citizenship by an American, even if that oath of citizenship includes a renounciation of citizenship, does not by itself strip an American of his citizenship.
See Action SA V. Marc Rich (Yes, Bill Clinton’s Marc Rich) for the latest case law on the subject:
http://openjurist.org/951/f2d/504/action-sa-v-marc-rich-and-co-inc
Nobody in the world could take Obama’s US citizenship from him before he turned 18. And after he turned 18, he himself could only get rid of it with great difficulty and clear and explicit intent.
When will we see Obama’s original long form birth certificate?