There isn't one. I think because there's so many north americans here in general. But I know other countries have one - i.e Norwegian students in Ireland, Ukrainian students in Ireland, etc. Might be useful. But it'd have to be separated into full course students and erasmus students because there's so many junior year abroad people here from the US/Cananda.
The easiest place to start one would be something like Facebook - and then once it caught on, tangible meetings could start