Separation of Church & State
The US Constitution established religious freedom: government should not interfere with religion, or vice versa.
The freedom to practice one's own religion, or to practice no religion, is at the core of the the American democratic experiment.
This principle is enshrined in the American Constitution. Most Americans agree that governments should generally not meddle in affairs of religious communities, except where there is a compelling interest. At the same time, particular religious doctrines should not influence government policy at the expense of people with different beliefs. To put it another way, maintaining a separation of "church and state" prevents some belief systems from dominating others.