My understanding is that those hirings are getting rarer and rarer, but I know every school is different. My university (ranked in the 70s for English, and in the 50s for undergrad) has one prof from Trinity Dublin, and everyone else is from a top 25 US program.
Often, if you're from a lesser known institution, it's more difficult getting manuscripts read or articles seriously considered. It's terribly unfair and pathologically elitist--but then again there are just far too many of us (aspiring scholars, that is) and it's a convenient way to eliminate a great number of potential applicants and job-seekers.
@Grizbert: I wish you the best of luck!