I see your point that the US is not completely militant extremist christian, however, the politics become more and more influenced by religious opinions. If you look at the politicians who are successful at the moment in the US, they all are, in my opionion, rather radical christian.
That's because most settlers who founded America were Christian, whether it be Anglican, Roman Catholic, or Lutheran (Which isn't really Christian, but very close). Most politicians are openly Christian because they want to connect with a certain group. To my knowledge, elderly and middle-aged people make up the most vote count, and, call it old-fashioned, but most older people are Christian because that was the usual religion for a long time.
Also, creationism is not proven or even plausible in ANY instance observed. Instead, darwinian evolution is proved to be the most likely explanation for the genesis of life.
People are stubborn. A lot of people going to give up their beliefs under any circumstance. It's simply a fact of life. In time, religion may become more or less popular and accepted, but it will always exist in some way, shape, or form.
As an example, Germany, where I live, has a strict separation of church and state. We nearly do not have any religioiusly founded laws. Germany is an example of successful secularism. On the other hand, bush famously said: "NO SIR, I don't believe that atheists can be good Americans as they don't recognise the values this country was built upon."
I didn't say, there are more and more christians in america, I just say they become more and more radical.
Again, if the people are religious, the government is also somewhat religious. The people in the actual government aren't asked to mix religion and laws, but if the people want it, then it will happen. As for Bush, he was a republican, and republicans are generally christian, conservative, and won't give up their beliefs. Bush also came from Texas, where people's roots go all the way back to Europe in the 1600's when atheism was unheard of. That was just one man's opinion, and, AGAIN, the PEOPLE voted him in, if they are Christian, then they will most likely support his beliefs.