Were there any specific areas of origin in England that were over or under represented? If so what were they and what was the reason for this disparity in representation?
The best way to think about early American colonists is to see them in terms of their individual colonies, which often had very different origins in terms of why they were settled, and thus, by whom. Many of these early colonies were indeed strongly associated with different parts of Britain and Ireland (not just England). A very popular (and good) book that deals with this exact question is David Hackett-Fischer's 'Albion's Seed: Four British Folkways in America' (1989), which aims to, as he puts it, 'explain the determinants of a voluntary society' (i.e. explain the origins of American culture and the differences between American regions.)
Hackett-Fisher identifies four regions settled by four groups, that I'll briefly summarise below, using the section titles he gives, as they're quite evocative.
The majority (60%) of settlers in Massachusetts who came in the great wave of emigration (around 20,000) in the 1630s were from East Anglia and surrounding counties: Norfolk, Suffolk, Essex, Hertfordshire, Cambridgeshire, Huntingdonshire, Lincolnshire and parts of Bedfordshire and Kent. This was a region characterised by high population density, relatively advanced agriculture and industry (e.g. textiles), high literacy rates, and a culture of dissent, both political and religious, most famously seen in the high numbers of Puritans there. It was strongly linked commercially and culturally to the Netherlands, from where many innovations (e.g. agricultural) came.
The Puritans left England in the 1630s, which was a time where they were religiously repressed, known by some historians as the Eleven Years' Tyranny, where Charles I ruled without parliament. After this there were no great waves of immigration to New England until the Irish in the 19th century, so the East Anglian Puritans made up the core culture of the area, and then 'Yankeedom' more broadly, for a long time after.
A majority of the colonists in Virginia originated in the south and west of England. This area is described as a much more class-bound, traditional, and undeveloped society (in comparison with the east of England) by Hackett-Fisher, that was recreated in America, with Virginia seen as a place for younger sons of gentry to go, especially in the 1650s when a 'puritan oligarchy' was in control of England. To recreate this class-bound society the gentry required indentured servants, who were recruited from the same region, with most departing from London or Bristol. This culture focusing on hierarchy, landed aristocracy and honour set the pattern for Virginia's development in the future. Governor William Berkeley, from this aristocratic background himself, is described as consciously moulding Virginia into the sort of culture he wanted, partly by shaping the process of immigration.
The migration to Pennsylvania and surrounding regions drew heavily on Quakers from the North Midlands (especially Cheshire, Lancashire, Yorkshire, Derbyshire and Nottinghamshire). William Penn, founder of Pennsylvania, was a Quaker, and Quakers also acquired West Jersey and Delaware for the specific purpose of realising their religious ideals in government). Emigration of Quakers to America was also seen by the King as a good way to solve the 'Quaker problem' in England. The 'Delaware culture' area then developed as directed by the Quaker ideals of its leaders, especially William Penn, who like Berkeley in Virginia, shaped immigration to the colonies he controlled.
The 'backcountry' (Appalachia) was settled primarily by English and Scottish settlers from the borderlands of England and Scotland, and from Ulster in Northern Ireland, where some of them had settled (or been settled) in the Plantation of Ulster in the 17th century (hence the name Scotch-Irish). The border regions had been lawless for centuries, but after the union of the English and Scottish crowns in 1603, they became less so, and the process of pacification and economic development worsened the conditions of many of the inhabitants. Those who had moved to Ulster also found themselves in a difficult situation, "caught between a rapacious Anglican elite on the one hand, and a fast-growing Catholic majority on the other" in Hackett-Fisher's words. Therefore many emigrated (some forcibly) to America, arriving principally in the ports of Philadelphia and Newcastle, where the Quakers, not wanting them to live among them, encouraged them to move inland into the mountains.
One region Hackett-Fisher doesn't talk much about, as far as I remember, is the lowcountry of the Carolinas and Georgia. The settlement of these areas began with Charleston in 1670, which was settled originally from Bermuda, with the aim of supplying English Caribbean colonies with provisions like food and wood. (This is from 'The Cambridge Economic History of the United States: Volume 1: The Colonial Era '). I don't have any information about the ultimate origins of these settlers in Britain and Ireland, but would be interested to find out.
I've only used Hackett-Fisher for these descriptions, so I'd like to know if there's any dissenting voices on his 'regional typologies'. Also I haven't really dealt with, because I don't really know, to what extent these founding groups chose the locations they were to settle in. E.g. did the puritans deliberately choose somewhere suitable for small scale family agriculture rather than large plantations? (maybe not, as they also established a colony in the Caribbean (Providence Island colony) that failed). Or did they just follow the separatists in Plymouth colony, who themselves had originally aimed to settle much further south than they actually did. And did the founders of Virginia choose an environment deliberately suitable for plantations? Probably not, as John Rolfe, who introduced tobacco planting, which was to become the economic basis of Virginia, was not among the original colonists. For the Quakers however, it does seem as though they did extensive research into the area they planned to settle.