If, as you state, "The founders intended that the beliefs of the People would continue to be expressed by its government" then what would prevent say, agressive Moslems from having the US gov express their beliefs and implement Sharia. I don't see how you can argue that the gov should express Christian beliefs but not other religious beliefs. I don't see any thing in the constitution that would allow one (Christian) but not the other (Moslem).
That is a non-sequitor. Any law must still abide by the Constitution and the Principles of this nation. While our democratic republic is based upon religious belief, religious leaders do not have the ability to dictate federal law. An Islamic community could lobby government to put up a monument bearing Islamic belief, but they cannot force others to follow their beliefs. Sharia is not established by the duly elected legislative representatives of the People, but by religious clerics. Thus, Sharia could not be *enforced* by federal, state, and local government agencies. Neither can religious organizations enforce Sharia with disregard to U.S. laws. Elements of Sharia would run contrary to the letter, intent, and spirit of our Constitution, thus it could not be upheld as law.
Incidentally, regarding the wording of the Constitution, the governing principles of our nation go beyond what some choose to recognize. It *includes* the intentions of our nation's founding fathers, and the spirit in which such words were written. Doing so otherwise would be to ignore context and definition, essential aspects of established law. It is akin to attempting to literally redefine "sex" and "marriage" to suit personal whims.