The problem that I see with mixing religion with politics in the United States is that this particular nation has such a diversity of religions because a variety of people have come here with them, mainly because we do keep religion and politics seperate. Living in Utah, where there is a seminary building at every school, somehow legally, I can definetely see how religion effects society and how a dominance of religion can throw things out of balance. A high percentage of the population in utah are members of the LDS church, and as a result of that people of that church are the ones who get elected, the state is republican etc.
Ironically, Salt Lake City, essentially downtown, is one of the most liberal cities in the country.
What I've observed generally happens here if you are not, what the slang term for it is, Mormon, you tend to get ignored. In school I was constantly bombarded to come to a LDS youth group, and after coming a few times I was asked not to come again because I asked some questions upon why the church didn't like homosexuality, what was so 'wrong' about it. After that, the mormon children, which was a large percentage of the school, ignored me. There were also a lot of non mormons who tended to not believe in any religion, or they were wiccan or some odd religion like that. Those kids tended to get into drugs and such. There's a major drug problem in Salt Lake City, despite it's liberalness.
At grocery stores even, mormons will not talk to non mormons. My sister was even told by a few of her friends in elementary school growing up that they couldn't be friends with her anymore because she was not mormon.
I also neighbor a street full of polygomists, even though it's illegal people know it's there. The church claims to be against it but they are actually supporting it.
Due to the church, a lot of homosexuals get sent to Evergreen, which I have mentioned before, to be 'cured'. They use a variety method, one involving electric shock therapy to the genitials of men in order to turn them straight.
In my opinion, the mass representation of one religion, and only one religion, has negatively effected people who are not that religion or are percieved as wrong by the church.
If religion were to be incorperated into politics ( which I hope that will never happen), there must be a way to balance the religions represented, just like the USA government has three branches to keep everything in check. Every religion would need to be represented. I just fear that most religions base their beliefs on the bible, and since athiesm is only one religion, the opinion of those who do not believe in any form of God would be overshadowed and not heard.