Obama has shown that he was born in the US in fact I have something which supports that:
According to you, your source is you dad.
Obama is much worse than Bush. I'm telling you, all Christian presidents were definitely better than non-Christian presidents like Obama. Even Bush, or Lincoln, or Washington, or Adams, or Jefferson, Madison, and Monroe.
It matters because its written in the constitution who is allowed to be president. The reason behind it is to ensure the president has the country's best interests at heart. That is less likely among foreigners.
It doesn't have to be as extreme as Sharia Law. Just literally any leaning towards charity for a particular group (lets say the poor) could be predominant in a Christian for instance. It still is unfair to lean that way to the rest of us. Maybe he leans toward a particular punishment less (like death sentences) because he's atheist, or more towards them because he believes in afterlife or reincarnation.
His leanings are influenced by religion and by his beliefs. You vote people in by their beliefs. How would you be able to judge where he got those beliefs from? Probably just as soon as you disagree with something you'd label him a religious fanatic of somekind, im sure.