Some stores in the US stock it and Irish brands. We can order it online from Amazon, etc. But the price is high. Besides, everyone knows the best butter comes from Vermont just like the best cheese is from Wisconsin. I know this is true because I saw it in TV ads and it's against the law to lie in TV ads.
My dad used to make butter from the raw Jersey cow milk they bought from their neighbor. While the milk is marvelous, I honestly couldn't tell the difference between his and the Dairygold butter from the grocery store.
And for something completely different, but butter related... watch the movie Butter, with Jennifer Garner. It may not get the highest ratings, but it's entertaining. Set at the Iowa State Fair and centered around their butter carving competition.