Wegmans (a mostly Northeast chain, but I think they are moving south and recently opened stores in VA) tend to have a large international section depending on the individual store. I used to get Mr. Moggs PG Tips, his jams, those dry chocolate dipped peanut cookies, and other things there. The cool thing about Wegmans is that if you ask for something that's not there, they will more than likely stock it, at least to see how well it sells. International foods might be a bit harder for them than domestic ones, but from what I've seen, British food at Wegmans was actually cheaper than British food in London.
I can honestly say that the only retail store I miss in the UK is Wegmans.