Why is the United States so religious, and how does this stem from its colonial beginnings?

Ever since the earliest days of colonial settlement, America has enjoyed a reputation for religious freedom. Although we take such a principle for granted nowadays, in the 17th century, it was a different matter entirely. In those days, your religion was largely determined by the ruler of the country in which you lived. If your religion was different from your ruler's, you could find yourself in serious trouble. Persecution, intolerance, and even execution were the order of the day for adherents of minority religions.
No wonder, then, that America and the "New World" seemed like the answer to so many persecuted believers's prayers. Here was a land where—for most people—it was possible to worship in peace, without the fear of persecution. As there was nothing quite like it anywhere in the world, America became for many a godly land, a place set aside by the Almighty himself for his "chosen people."
This explicitly religious notion of America as "God's country" gradually fed into the political self-image of the newly independent United States as a nation apart, a special place endowed by the Almighty with the blessings of freedom, opportunity, and material abundance. Because of the close links forged in the 17th and 18th centuries between God and the blessings of liberty in American political discourse, this picture of the United States still retains a powerful hold on the American imagination to this day.