There are people who through their actions would impinge your freedom of conscience, muzzle your self-expression, violate reason, and stifle others' imaginations and innovations. To prevent these people from ever having the authority to perpetrate this great violence upon American democracy, the separation of church and state is essential.
We are not people to casually cast aspersions. We do not hate blindly or reflexively. We form opinions of people - individuals and groups - over multiple exposures to their beliefs, attitudes and intentions as revealed through their statements and behavior. I have heard and seen enough of the beliefs, attitudes and intentions of religious extremists of several faiths to know that they pose a severe threat to us all. This is an issue that you need to be knowledgeable of - no problem-solver, no leader of women and men in your generation will achieve anything without understanding the perils of religious radicalization, at home or abroad.
In the American context, the chief violators of the separation of church and state are conservative evangelical Christians. Before proceeding any further, it is of the utmost importance that you understand the limits and sensitivities of using stereotypes to judge all people belonging to one identity group. There are no doubt multitudes of cheery, well-behaved people who believe the Earth is roughly 6,000 years old, that all life was cut out of whole cloth by an all-mighty creator (with humans in that creator's image, of course), and that all of humanity is soon entering an "end-times" in which the truly righteous will be whisked to eternal salvation, while the rest of us who actually seem to care about each other and this world will be "left behind" to endure the apocalypse. No doubt many such lovely, thoughtful human beings exist. All other things being equal, it would serve no point to casually group all such believers together and publicly disparage them. But when the matter at hand is whether children ought to be taught how to think critically and scientifically through exploring the empirical history of life, the universe, and everything OR taught instead that Jesus really loves them and God made them just the way they are ... and not to worry about the panda's thumb, or mitochondrial DNA, or any of those silly little rocks - it is by all means acceptable to stereotype these people negatively. Holding such a negative stereotype in these circumstance neither darkens your character nor reduces your credibility.
When dealing with people whose perception of the world is so radically skewed from empirical reality, you must not fear political correctness. There is no equivalency between not hurting their feelings and letting them erect their little-god-centered idiocracy. When their insouciance is at its most loathsome - ridicule them for being bigoted, parochial, vengeful, and just plain ignorant. You may also choose to ignore them, but that won't change anyone's mind. If they really believe what they espouse, then they must wish suffering and death upon the overwhelming majority of human beings alive. And that is a wish unforgivable.
If you catch many of the same unflattering views of the religious right that I have seen, then you might conclude that they are parochial bigots fighting a rear-guard battle against the efflorescence of human life and potential - writ large. Many decades ago men started to come around to the idea that woman are no less intelligent or capable in life than they are. Not since before my birth was it acceptable to espouse and practice racial bigotry. Homosexuals still battle the powers of prejudice and disapproval for fair treatment. As each of these injustices has been slowly - and happily sometimes briskly - eroded, a bulwark of dogmatism has stubbornly withstood all temperate and better counsel. It is still acceptable in many peoples' consciences to automatically discriminate based upon religious belief - or its absence; both options seem to be the primary animating forces behind conservative evangelical Christians. It doesn't seem to be what they believe that is all that important; since most of it is demonstrably false and at least some of them, deep in their consciences, must know it. What seems to be important is that YOU believe something other than theirs or that YOU don't believe any of the pre-packaged, previously sanctioned options. In a nutshell - other religions and the option of disbelief. I'll let you finish the thought of what's just so terribly wrong with this state of affairs.
There is no doubt that American society will remain religious for generations to come. This is a source of strength - but as the struggle for a form of governance unladen by religious confusion shows, it is also a complication. We tend the separation of church and state to mediate this inherent tension in our society. The most egregious threat to the delicate balance maintained by this elegant maxim of governance is the religious right, which I described in rough but sufficient detail above. Whether you choose to focus more on one side of this tension or the other - strength or complication (or if you're a perfect heir to my congenital indecision, and thus not a little thought or your own on the matter) - just remember that American religiosity and the separation of church and state are bountiful subjects for exploration and, yes, even some modest commentary.