The New England Historic Genealogical Society (NEHGS): www.americanancestors.org in Boston is a treasure trove of records and assistance. This is the oldest and perhaps most prestigious genealogical societies in the country founded in 1845. While their main focus would be the New England states, their collections are by no means limited to that area. They have material on Virginia, Canada and of course Ireland.
Their library collection consists of over 12 million books, manuscripts, family papers, Bibles, electronic resources, photographs and artifacts documenting some four centuries. The expert staff can consult and assist with many ethnic and geographic regions. Among these are New York, French and Atlantic Canada, African American, English, Irish, Scottish, immigration, Native American, military and New England. All of these have some application to your Irish research.
Of particular interest for Irish Studies is their Irish collection of books, microfilm and digital resources. They have an interest in the Scots-Irish as the first wave of Scots-Irish to the colonies came from the Aghadowey Presbyterian Church in County Londonderry. These immigrants left in 1718 and founded Londonderry, New Hampshire. The NEHGS library has a transcript of the Session Minutes from the congregation 1702-25 which documents many of these early immigrants.
The society also publishes several top quality publications. These include The New England Historical and Genealogical Register; the American Ancestors, and American Ancestors.
For your New England and your Irish research, do not neglect the NEHGS collections as a major resource. In fact, they are certainly worth joining as membership will provide you will online access to their large collection of indexes and databases. My personal favorite is the “Search for Missing Friends: Irish Immigrant Advertisements, 1831-1920” (from a Jesuit newspaper) which I use on a regular bases.