Church attendance/census records show we're probably no less a religious society today than anytime in the past. The writings of the founding fathers show some distinctly different interpretations of Christianity and religion than that portrayed during the Reagan years (and during the revisionist Currier and Ives period). Our one true national religion, free market capitalism, is still going strong.
The pledge of allegiance and the powerful symbol of the flag, as we know them today, grew out of fear over the waves of late 1800s immigration from Eastern and Southern Europe. They were seen as lesser Europeans, not committed to the same pure principals as the people of good Western European stock (sound familiar?). Some were anarchists, who committed acts of terror and attempted the assassination of Teddy Roosevelt discussed in a recent thread. Tools were needed to get them with the program.
In a wave of national patriotism, our national embarrassments (a mild word in some aspects), such as the Indian Wars and slavery, were sanitized. The unnecessary (except from a colonial perspective) Spanish-American war became a heroic epic. George Washington "cut down the cherry tree" but no one noted that he could have just had one of his slaves do the deed. History and patriotism were polished, packaged and presented in simple, feel good ask no questions terms.
The pledge was adopted in 1892. The flag, which had really been a non-symbol up to that time (and even until WW2, largely) was suddenly emphasized (in fact, we used to salute the flag in the Zieg Heil manner until WW2 prompted a change).
That is why I have a really hard time with any constitutional amendments over these symbols. I don't personally pledge allegiance to the flag, like some Nazi or Communist was required to by the power of the state. My allegiance is to the freedoms outlined in the Constitution. I had no trouble with this pledge upon entering the armed forces, and don't to this day.
The separation of church and state is part of those freedoms. A part that is perhaps hard to understand by the religious majority -- or at least inconvenient.
Some Christian sects (such as the Southern Baptist faith in my personal background) are very much focused on converting non believers to the one true faith, and will lever any possible opportunity to convert children in the public schools. This is no secret. Ralph Reed, formerly of the Christian Coalition used to brag about how clever he was in “stealthing” Christianity into the public schools through school board elects, etc. Now, there are evangelical Christians who see these actions as good deeds, that will ultimately save America from itself (whether we feel we need to be saved from ourselves or not). I see this as a threat to our way of life that is greater than anything a pissant like bin laden could come up with.
Further, many religious people, regardless of their aggressiveness or particular faith, see no problem with non believers generally being required to acknowledge a God, even if they would never stand for their children having to acknowledge the special divinity of another religion. But of course, nobody is "required" to say the pledge.
My stepsister is teenager in the Bible belt. Both her and my stepmom are religious, but they were not churchgoing. That is, until my sister started to get a hard time from her peers for not going to church. She was increasingly becoming an outsider in some very apparent ways, so she got with the program eventually. I don't think it was a big deal for her (being a believer in general) and it made her part of the crowd and probably increased her social life. However, for someone with perhaps deeper convictions, I really can't imagine being the only person in a High School class not to stand up and say the pledge without feeling tremendous pressure to get with the program. And, this type of "coercion by example" has no more a place in a public school than a pledge saying: "one nation without god" or "one nation under Alla (or Budda, or Hitler, or Jesus Christ)
Charon
[edit: The Senate vote seems to show the impact of coercion by example as well

Who wanted to be the first one to vote nay, since the reasons for voting nay wouldn't fit into a typical soundbite and would likely be lost on their constituents, many of who don't know which side of the war we fought on in WW2, for example.]