Is Irish Bacon like regular bacon, but with Guinness?
No, although I'm tempted to add that to my brine just for the sake of science.
In other parts of the world, American Bacon, which comes from the pig's belly, is called streaky bacon. Another European variant of it would be pancetta, which uses wine in the curing process.
However, in England, Ireland, and Canada, you also get a food called "bacon" by curing some of the back muscles of the pig (typically, I use pork loin when doing this). To distinguish them from streaky bacon, these back bacons tend to be referred to by their country of origin while in the states. The cure for Irish Bacon typically includes molasses, and may or may not actually involve smoking the meat (I don't mostly due to a combination of time and not having a good place to smoke it).
It is actually far more authentically Irish than corned beef is (which is actually Jewish American). Historically, cows were for the wealthy in Europe, thus, Irish Bacon being far more common as a peasant food. When the Irish came to the US, they were looking for something similar to the bacon they had back home, and turned to their new Jewish American neighbors, who it turns out didn't do pork. Thus, why "Corned Beef and Cabbage" kinda gets lumped in as the stereotypical Irish Meal.