That is very interesting. Would you please elaborate. What style of American beer might cause that reaction?
Until a couple of years ago the only American beers that where available in the UK where the classic big brewery, no flavour ones. The general opinion of American beer had been created by these tasteless and rather pointless brews. More recently a few decent American beers have started appearing (SN Pale Ale being the easiest to find) but most people who like beer automatically group all American beer with the Budweisers of this world. Once you persuade them to try an APA or a DIPA or whatever there is a moment of revelation....
We now have one easily available UK brewery that is making the newer styles of beer (BrewDog) but this is only just becoming available in major retailers..