The group historical blog Cliopatria and History News Network will soon post an online symposium on the question, "Why has the American national narrative characteristically taken New England/Puritans [first settlements 1620 and 1630] rather than Jamestown/Virginia/Anglicans [first settlement 1607] as its foundation touchstone?"
My first answer is simple: because the North won the Civil War. (Hey, nobody said it had to be a good reason!)
Here's another answer, from Paul Noonan in the comments:
"At Plymouth you have a family-based society of hard working humble folks who seek freedom to worship God in a way their society doesn't tolerate. They persevere in the face of great hardships.
"At Jamestown there are also great hardships, but there you also have an initially non-family based society (the original settlers were all men and for well over a decade the colony was a mostly male frontier society). Their religious sentiments were conventional; their motivations in coming to the New World had to do with economic opportunity (initially a delusional search for precious metals; later the growth of tobacco, an agricultural product with no nutritive value and - as we much later found out - actually deleterious to health). The early settlers were mostly 'gentlemen' who at one point had to be threatened with having their rations withheld in order to get them to do a decent day's work."
If you'd rather think before opining, Cliopatria has links to reading material. And if you prefer books to blogbytes, my fave on Virginia is Edmund S. Morgan's American Slavery, American Freedom: The Ordeal of Colonial Virginia.