Judging a sentence right from wrong is by grammar not by adding something to it. The original sentence is correct grammatically, as I suggested in my first response. We added things to it to bring out the meaning,
1.” Nowhere else in colonial America (i.e. nowhere but in New England)”-----I don’t know why you don’t say but in China?
Because the writer was talking about new England, not China!
.2.Accoding to your explanation,” Nowhere else in colonial America (i.e. nowhere but in New England) did people attach so much importance to intellectual pursuits.”, you have changed the object of our discussion.
No I haven't. 'Nowhere else' has meaning only in the context of the preceding sentence, which mentions New England.
3.In the original sentence, “nowhere else” is the subject, ,”importance” is the complement, and “attached to …”the attributive of “importance”. In short the one is “ Nowhere was importance,” which can you think is right? Nowhere else' is not the subject; 'so much importance' is the grammatical subject of 'was'.