What groups of Irish made up the first Irish Immigrants and what was their role in early American society?

The first group to immigrate to America from Ireland was the Scotch-Irish (ethnic Scots colonists in Ireland) in the 1700's. These Scotch-Irish where predominantly Presbyterian's who left for a better life from the discrimination of the Church of Ireland which tightly controlled the island as well as for economic reasons..

These Scotch-Irish form the backbone of American society, with many famous Americans such as Davy Crockett, Dolly Parton, and at least a quarter of US Presidents (Bill Clinton, Ulysses Grant, Theodore Roosevelt amongst others) having Scotch-Irish roots.

These same Scotch-Irish became great pioneers taming Appalachia and west. They contributed greatly to George Washington's side in the American War of Independence and also to both sides in the American Civil War.

The Seal of the United States, the draft of the Declaration of Independence, alongside many other things that are quintessential to American heritage where done by Scotch-Irish.

Blue-grass music was also developed by these people which later progressed into country music.

Even the term red-neck can be attributed to them, with it arising from the Presbyterian's in the southern states use of a red scarf around their neck to protect it from the sun.