It doesn't work so well in practice though does it given the numerous articles posted here about politicians trying to bring creationism into classrooms?
I, honestly, don't know if the "creationism in classrooms" was ever brought into public schools (Government funded), but I know it's taught in a few private religious schools (of which, aren't part of the government). I can see something like this being passed in some of the Southern states, given their tendency to lean towards such fundamentalist Christian thinking (As can be seen with some of the changes the Texas School Board wants to do to textbooks). And there are current laws that exist from a Christian background, such as DOMA for instance. However, I'd say that having a doctrine that advocates "Separation of Church and State" is better than not having one at all. Otherwise, movements to actually stick creationism in classrooms on a national scale would, likely, go through with much more ease, and from no clear-text stating such a separation, minority religions and persons in the US would likely become the targets of laws created out of the Christian mindset (Christian, specifically, as it's the dominant religion of the country and has notable political sway).
For the LGBT community, the Christian involvement with politics is more worrying than to others due to the support a lot of bills (and support from even Presidents) to keep marriage as a separate institution, and even keeping adoption away from the LGBT community. Which, naturally, means that LGBT couples (Even Civil-Unioned ones) have less rights than the married counterparts, which in my viewpoint, is discrimination and this discrimination is held in Christian fundamentals and held together with the discredited "findings" by a psychologist named Paul Cameron. (I believe it was a "Paul"). In every legal debate I have seen, this psychologist's claims are often used (which were biased) and the fact that these opinions were discredited by the American Psychological Association, and a plethora of others, and the fact that Paul Cameron is often referred to as a mockery of psychology (basing that opinion on discussions I've had with psychologists, along with their articles at times) doesn't come up in these debates.
In a perfect world, there'd be no religious bias in politics. However, this isn't a perfect world and there is a notable bias in religion with Presidential candidates, Presidents, Congress members, Senators, Governors, Mayors, Judges, and so on and so forth, which leads to it being brought into politics (often times, citing pseudo-science as fact).
But, it is better to have it a bit more "controlled" than for it to run rampant. I've heard some leaders of those "traditional family" organizations say that they want a theocracy, and would want to kill all the "heretics" and all the "gays" or to separate all of them from society. (And would likely, bring back the witch hunts of the 1600s -- I believe that the author of the ludicrous book "The Pink Swastika" was one such person). So even though there is some religion in American politics, I'm happy that it's not as rampant as it could be.
