Secularists are threatened by that, for some reason. They're a confused and conflicted lot.
I wanted to handle this particular comment separately, because it seems like you're trying to indicate that non-Christians in this country (secularists and people of other religions) don't have a reason to be concerned about the Christian push to be a Christian nation. I don't think you are. I think you understand full well why people are concerned by that, and are just playing devil's advocate, there. But just in case, and for those who actually don't understand it, here comes a somewhat long-winded post.
Human history is replete with the kind of destruction, bloodshed, bigotry, hatred, jealousy, war, persecution, death and oppression that religion has wrought since the moment one human said to themselves, "Hey, there's a bright, shining warm ball up there that lets me see and warms me up. I can't explain it, so it must be some kind of supernatural being."
It was perfectly understandable, in a time when science was utterly unknown. People didn't understand how things happened, and as a species we all struggle to understand the why of things. But "how" and "why" are two different things, and "in the beginning" we weren't capable of understanding the "how" and could only ascribe to things the "why." And if we were unable to come up with a causality that could be attributed to ourselves, then it must have meant some other person caused it.
So we made the great leap from self to deity as the causation - why did we have that earthquake? Because someone else with the power to cause earthquakes was angered by us. Not because, as we now know, techtonic plates moved and the resultant waves of energy became an earthquake.
As the years went by, people began to question and discover the "how" things worked and not just the "why."
As an example, here are "how" and "why" questions on the same subject.
How are we here? According to science, billions of years ago the conditions were right for the formation of the first organic compounds, which eventually came together to create life through the process of abiogenesis. Without going through an excruciatingly long description of the beginnings of life on earth, suffice to say that science tells us that once life began on earth, it evolved and spread, culminating in what we have today.
Why are we here? Because.
Which I admit is really an oversimplification. I'm trying to be as brief as possible, becuase this is going to be a long post, but it gets the point across, I think.
And it leads into my first point with regard to the "why" of why many people feel threatened by religion in general and Christianity in specificity when it comes to the US and claims that we're a "Christian nation."
One of the issues - especially for secularists and Atheists - is the attempt by Christians to insert the teaching of unscientific belief as scientific truth or an "alternative" to what is scientifically known. The best example is the teaching of Creationism in public schools. Thirteen states and the District of Columbia have at least some schools where Creationism is taught as an alternative to science and evolution.
The trouble is that Creationism is not, despite the best efforts of some, a theory, or even a hypothesis. It's a religious belief that requires faith that someone (in this case God) simply wished or magicked the universe and everything in it into existence, and it's a belief that has been forced into science classes as an alternative "theory" for the creation of earth and the life on it, by lawsuit.
This is just one example of the religiously faithful attempting to (and succeeding in) force their beliefs into an area where they do not belong - in this case a public school science class, where what should be taught is science, not dogmatic belief that requires no evidence.
Yet another example is the flap over same-sex marriage. The entire foundation of the fight against same-sex marriage is religiously based on six scriptures in the bible.
The story of Soddom and Gemorrah in Genesis 19 refers to the
threat of gang rape. If you actually read that story, no homosexual acts are committed, and the infraction is that the men of the city threaten gang rape on the angels (who were, albeit, disguised as men).
Then there's Leviticus, where God twice condemns homosexuality. But there's a sting in that tale, and it comes in Romans, where Jesus says he's here to fulfill the law (we've had this argument in another thread already, and I've made my position on what Jesus did or didn't do pretty clear there, but the argument Christians use here is negated by Romans, which Christians also use to claim the Old Testament laws are null and void, so I thought it worthwhile to mention).
It's interesting that Jesus says he's "fulfilling" the old laws but then in Romans homosexual acts are condemned again.
But that's really all there is to it. Six times homosexuality is condemned in the bible, and that has been the foundation upon which centuries of hatred, bigotry, bloodshed and murder of homosexuals have been allowed to flourish.
There are even some (remember that little ballot proposition in California last year?) who believe homosexuality should be punished by death.
Fast-forward to the Supreme Court's ruling on what really was 14th Amendment protections and not really same-sex marriage. The old religious arguments against homosexuals were used right up to the Supreme Court in order to attempt to use the Constitution as a weapon of bigotry against an entire group of people - all for those of a religious bent to condemn others while claiming to be Christian.
It's also very taboo to speak out against religion, and it shouldn't be.
Religion, while responsible for a lot of good, has also been responsible for countless acts of barbarism and violence (need I dredge up ISIS, the Crusades or Cotton Mather?), and yet any criticism of it is immediately tamped down. Even today criticism of religion can mean death (ISIS and the middle east again), but why?
The main religions, especially Christianity, has rather a LOT to say when it comes to criticizing others - at least those others who do not belong to the same religion - and that's deemed right and proper. But if someone comes out against something a religion has done or said, that someone is shouted down by a righteous and angry mob of whatever the religion may be. And then others rise up who are NOT of the same religion with the general feeling of, "Hey, you can't talk about X religion like that!"
Religion gets a lot of leeway when it comes to criticizing others, but its followers don't give any when it comes to having their religion criticized.
Faith is defined as belief without evidence. You must be willing to set aside reason and logic in order to be "fully" faithful. Many of us aren't willing to do that - I'm certainly not, and am yet still a religious person. I'm just not "blindly" religious.
And it is the blindly religious who screech the loudest, who try with all their might to insert their own beliefs into the law, who want their religion to BE law.
I could go on for many hours about exactly why (AND how) so many people are threatened by religion - especially Christianity in this country.
I have put forward just a few of the reasons, and there are so many others. Those who understand will get it. Those who do not
want to understand won't.
But you are not unintelligent, so it surprises me to see you say that people feel threatened "for some reason" by Christians who claim we're a Christian nation, or demand we be so.