There's no way Hinduism has one of the lowest conversion rates in the United States. No one born in the United States actually practices that religion; they all turnout as atheists/agnostics/apatheists/whatever. With such a wholesale rejection of Hinduism ('rejection' isn't really the right word, since the attitude is too apathetic to be construed as such) I don't know how you can arrive at the conclusion that Nikki Haley and Bobby Jindal are somehow unique in terms of defying their cultural heritage of whatever.
Sure I see a lot of Indians born in the states who don't practice Hinduism, me being an example I suppose, but I've yet to meet anyone who's actually converted to Christianity. Because of that Christianity, I think that Haley and Jindal are unique.