Here are some highlights from this 2004 book by Eric Kaufman:
* Even as late as the 1960s, 90 percent of white Protestants, Catholics, and Jews married members of their own faith.
* I single out cultural and ideological changes originating from within the Anglo-Protestant community as the primary engine of dominant ethnic decline.
* Wilbur Zelinsky describes this phenomenon, as it pertains to cultural geography, as the doctrine of First Effective Settlement, whereby “in terms of lasting impact, the activities of a few hundred, or even a few score, initial colonizers can mean much more . . . than the contributions of tens of thousands of new immigrants a few generations later”. David Hackett Fischer’s writings outline a similar theme. He notes that the United States began as a collection of cultural regions based around core English settler ethnies. The Puritans dominated in New England, the Quakers in the Middle Atlantic states, southern English Cavaliers in the coastal South, and Anglo-Scottish Presbyterians in the Appalachian hinterland…
Since most of this “colonial stock” had arrived in the seventeenth century from Britain, it is not surprising that on the eve of revolution the American white population was over 60 percent English, nearly 80 percent British, and 98 percent Protestant.