I thought the whole a/an debate was pretty clear cut, but after reading a recent CSC report (www.csc.com) on outsourcing, I'm not quite so sure. Checking the archives reveals that belM wrote 'an U.S.' once here.
I think it is agreed that "an" should be used before a word beginning with a vowel sound, however the word is spelled, and that the 'h' problem is a matter of prerogative/pronunciation. So what is the consensus on this odd sounding one:

"... outsourcing is based on an U.S. perspective."


p.s. We've had this topic? - Oh, well. Where's the link? :-)