This is of course simply false. While Puritan ancestry is found at higher levels among Mormons than in the US population in general, it's not true that Mormons today are of predominantly Puritan descent. (Nor is any other major population in America today of predominantly Puritan descent.)
In addition to Scandinavians, converts from missionary efforts in Britain form a major component in the ancestry of those with early Mormon roots. Moreover, most of the British converts came from areas outside of East Anglia and should tend to be "clannish" relative to New England Puritans in the JayMan understanding of things.
Hail, looking at Mitt Romney's ancestry, found:
The current president of the Mormon church, Thomas S. Monson, has no colonial American ancestry whatsoever. He's half Scottish, 1/4 northern English, and 1/4 Swedish.
- Most of his ancestral stock consists of early converts to Mormonism from Britain (most from Northwest-England and Scotland) who were impelled to the USA from the 1830s to the 1850s, settling directly in Mormon communities.
- Colonial-Yankees account for 27% of Romney’s ancestral stock.
- 12.5% (one-eighth) of his ancestral stock comes from Northern-Germany.
What makes this all even more amusing is that Glenn Beck was not even born a Mormon. He's a convert, and per wikipedia:
He is descended from German immigrants who came to the United States in the 19th century. Beck was raised as a Roman Catholic and attended Immaculate Conception Catholic School in Mount Vernon.
Glenn and his older sister moved with their mother to Sumner, Washington, attending a Jesuit school in Puyallup.