Have not been to Ireland but had the same experience with Guinness at the Irish pubs in Boston. It also took them a LONG time to pour one. Has to do with the transport as well(biggest factor).
Found this:
Why Guinness Tastes Better in Ireland (& More Surprising Guinness Facts).
"Some people think there's a different formula for Irish vs. American Guinness, but that's not true. According to
Slate, the key factors are really time and distance. All the Guinness that's sold in the UK, Ireland, and North America is made in Dublin."
"The perfect pint of Guinness is poured with the glass
held at a 45° angle. It should be left to settle on a flat surface for 119.5 seconds to let is "surge" and allow that perfect, foamy head to appear."
So basically distance traveled. Also better where more is served, so fresher kegs. Makes since why it really does taste better in Boston than Tennessee.