I've been to Ireland twice...and we drank Guinness everywhere from small town pubs to The Storehouse (the pub on top of the Guinness brewery at ST James Gate) and never was it served warm. The REAL problem is, in the US most bartenders don't pour it properly, and it makes a difference, really it does. If they are not busy, you can ask the bartenders at the Rose and Crown to let it rest for a proper pour.
Here in the southern US, a black velvet is Guinness/hard cider.