2. Equality of the masses
While religions will often define the "correct" masses as a certain subset of their population (e.g. one gender, one race)- all religions exist on the premise that these masses, as defined, are equal amongst themselves. Often this is classified as a powerless equality, and often this equality comes with few or no fringe benefits during a member's time on Earth- but, regardless, it is equality nonetheless. American democracy, which is inspired heavily by capitalism, requires inequality to succeed.
3. Expected salvation
In religion, it is expected that all participants will achieve some form of globally-defined salvation- having all of one's existence being "made right." Salvation is there for everyone, in exchange for obedience and participation in simple- often thoughtless- rituals. The differs entirely from the methods of achieving goals in an American-style democracy, methods and goals which all law is built to protect, and even encourage. In America, it is each individual's responsibility to define salvation for themselves, and work to achieve that salvation through personal ingenuity, and physical or mental work.
- AN ESCAPE OR RULE OF LAW? -
None of this is to say religion is inherently wrong. While its rules and standards directly contradict any system of rules and standards that actually works, religion does have its place in a democratic society. Hence, the architects of American democracy did not prohibit religion. They did, however, specifically guide our lawmakers to ignore it (read: separation of church and state). And there is a reason for this.
Religion, you see, is an escape. Much like sports, people use religion as a controlled microcosm of life, which they can visit and surround themselves with at any time. It exists separate from the often confusing real world- where people have the ability to do practically anything they want, and often suffer perplexingly contradictory effects from such actions. These escapes provide clarity to their participants because the participants have no direct involvement in the rights and wrongs, nor the outcomes of such rights and wrongs.
The problem with religion is that in its attempt to describe and stipulate eternal rights and wrongs, it is easily mistaken for being inherently above the law. The rules of baseball, for example, don't attempt to use strikes and balls to prescribe how judges, politicians, policemen, and the like should carry out their responsibilities. Religion, on the other hand, goes there.
No nation can succeed if its laws are based in the tenets of any religion. America's founders knew this, and the nation continues to evolve despite religion- which it has done a fairly good job, throughout history, of keeping at bay. However, the danger is that people's ignorance of what religion really is- a recreation, or at best an activity that exists separate from all of government- can begin to build an assumption that religion and government are supposed to exist together, and equally so. Or, worse- that religion guides government.
We may be one nation tolerant of God, but we should not be one nation under God.