Irish universities, like most universities, are very interested in recruiting overseas students. It means more money for them! Trinity is a fairly competitive school, so you'll want to check their website to find out what their minimum requirements are. Typically, I wouldn't be concerned about a degree from Ireland transferring to the US (most people I know have degrees in liberal arts or sciences), however, since you're looking for a specific certification in social work, you'll probably want to find out if the US will accept that qualification. I'd make this same suggestion if you were going into teaching or nursing.
One thing my husband said to point out is that as an international student you are required to show proof of health insurance when entering the country. They're pretty serious about this, and he's heard of students who are turned away if they don't have the appropriate documents. Ireland doesn't have a system like the NHS, so you have to be prepared prior to arrival. Also, Dublin is an expensive city to live in, so you'll want to consider your finances. But, it's a great place to live, very safe, and a lot of fun!
