When I first got here I was hitting an unknown word about every 2 hours. It really causes my brain slow down with the extra time it takes to process it. I hear all the right words but it just doesn't have sense so I find myself asking people to repeat themselves and they just say the same thing over again. The problem is that everyone understands me because of the pervasiveness of American Movies and TV shows so they don't relise I don't understand them. None of the British people I've talked to believe it is that big of a deal. The only people I get any sympathy are the ones that were taught American English in school (Taiwan and Chile at least) so they see all the same differences, but they (rightfully so) don't think it is as big of a deal as having the double problem of it being a non-native language and different accent.
When I have talked to some of the british people and they get mad for other British people not using the right words ("cello tape" instead of "scotch tape") they blame it on the American movies ruining the Queen's English. My argument has always been that there are two languages, British English and American English, and as long as they are seen as that there isn't a problem. I see as much as of a difference between American English and Scottish English as there is between Spanish and Italian, but because English is tacked onto the end people are expecting a similar language.
Sometimes it is just a different term, like saying excuse me (people don't move) instead of pardon. Some words I figured out what it was when I heard it (ladybirds = ladybugs). A lot of the words are when I go grocery shopping. If I can't find what I am looking for on the signs I'll think of what it would be next to. I found dish soap (washing up soap) to be next to the other soaps. A lot of vegetables are like this: Eggplant = aubergine, zucchini = courgette, cilantro = coriander, canola oil = rapeseed oil; so it just takes more time when I shop. (There are more, those are just the ones I've bought so far)
However all this cultural experience is all fun and games until I got hurt. When I flipped my bike I walked into a pharmacy (Chemist) on my way home when I saw my knee was bleeding pretty bad. I asked for band-aides and she stared at me, so I asked for rubbing alcohol and I saw her eyes dart towards the liquor store across the street. Frustrated, I finally asked for disinfectant and she pointed me in the right direction. I now know that band-aides = plasters here.
Also, I have been trying to pick up the right words from listening to everyone I talk to and movies. British English adds an "e" sound to a lot of words, so Television becomes Telly and present becomes presi. But, if I didn't know any better I would end up using the racial slur of calling Pakistani people Paki (from watching a British movie). A "telly" show that I did watch before coming here was "The Mighty Boosh" to try to learn some of the language. When I tell people here that they laugh since apparently one of the guys uses a lot of Irish words.
Another problem is that most european countries teach British English along with the British accent from a young age so just because someone has a British accent could mean they are from Belgium, The Netherlands or somewhere in Scandinavia. As far as my American accent, British people don't really have a preference (They prefer a strong southern Georgia accent) But the rest of the Europeans that have English as a second language can't tell one American accent from another so to them I sound like I have a drawl so they like hearing me talk. I've lived in enough different places in the U.S. to not really think I have an accent from any specific place so when people tell me that they like my accent it throws me off.