Actually, the Irish who created the whiskey industry in America were not true Irish. They were Scots-Irish (a.k.a. Ulster Scot), which is not the same thing. For one, the Scots-Irish were Presbyterian, which is a religion that was primarily practiced in Scotland during that period of time. True Irish men and women were Catholic. True Irish did not arrive on our shores in considerable numbers until the potato famine, which occurred in the nineteenth century (Catholics were only truly welcome in Maryland during the colonial period, which George Calvert, a.k.a Lord Baltimore, established as a Catholic sanctuary). On the other hand, the Scots-Irish landed on our shores in large numbers during the 18th century, some as early as the 17th century. The Scots-Irish were actually originally from the border between lowland Scotland and northern England. They were mostly border reivers (border raiders) and other assorted problem children from the same area (the border was lawless). Oliver Cromwell transported these trouble makers to Ulster Plantation in Northern Ireland. A large number of Scots-Irish men (usually prisoners of war due to having served as mercenaries who were difficult to control) and Scots-Irish women were eventually transported to the American colonies from Ulster Plantation and sold into bondage as indentured servants (for example, Campbell, as in Glen Campbell, is a border reiver Scots-Irish clan name). Many of these indentured servants ran away to what was then the western frontier; namely, the hills of Appalachia (a place that was not safe because it was populated by Native Americans who were hostile to colonists). The term "hillbilly" is a contraction of "hill" and "billly." A "Billy" was a Scots-Irishman (after King Billy, William of Orange).
A big distinction between between American whiskey and Scotch/Irish whiskey is that American whiskey is made with a grist that is primarily grains other than barley. These grains may be malted or unmalted whereas Scotch and Irish whiskey are made primarily from malted barley. The grist for Straight Bourbon needs to contain at least 51% corn and the grist for Straight Rye needs to contain at least 51% rye. Bourbon and Tennessee whiskey were created by the Scots-Irish in Kentucky and Tennessee (Kentucky was part of Virginia and Tennessee was part of North Carolina during the colonial period). Rye whiskey was created by Scots-Irish in Pennsylvania and Maryland. I am a BJCP certified beer judge, and I made all-grain beer for over twenty years. Whiskey is basically distilled unhopped beer, which is why I am familiar with the process. There is a huge overlap in the skills necessary to produce beer and whiskey. They both use the same process to convert starch to sugar (a.k.a. "mashing" or more technically, the hydrolysis of starch).