I would say that the presence of Enlightenment thought played a large role in transforming the relationship of church and state in North American Colonies.  The assertion of the role of the individual in Enlightenment thought was largely responsible for the growing secularism in Colonial culture.  Due to this, Colonists started asserting their own freedom in a manner that was not necessarily tied into religious thought.  Figures like Ben Franklin emerged out of Colonial culture, individuals who were not necessarily tied to religious worship as much as individual endeavor.  As this secularism started to take hold in the Colonies, it started to raise political ideas that the Colonists found attractive.  Ideas related to the social contract between ruler and ruled and Locke developed and the idea of defending individual rights at all costs from Voltaire started being disseminated and shared amongst the Colonists, further enhancing the secularism that was already playing a defining role in Colonial culture.