Check out setanta.com They own the rights to most international matches. Your cable company may offer setanta. And setanta streams game online. There are bars (banshee) that play games in Boston. For big matches expect to pay a cover as these are pay per view. Big money internationally. Probably why is hard to catch on the US. If this was free to watch, maybe people would get into it.
I've never heard of superleague being televised. 7's (7on7 rugby) is occasionally on TV, I think the day of the superbowl.