I get it all the time even though I try to pronounce things a little different to avoid such situations we are all too familiar with the oh I love your accent.
Popped out for an onion for dinner the other night as I'd ran out, the guy at the register was positively drooling as I chewed my son's face off for something then proceeds to tell me how all his family are Scottish. I seriously wish I had a dollar for every time I heard that one.

I just worry I'm going to go back to the UK and forget to switch back and end up sounding like an american. For some reason, I think that would really offend my english friends/ family. Or even worse, I might be mistaken for being american.

Yup you do and the female is a hen turkey not a hen like in chicken

Pedagogue

If your friends would be offended because you modified your speech to communicate in a foreign country, they're not worth having.

You will probably end up with a mid-Atlantic accent, but it will go away quickly when you are back.

Probably because you are expecting their accents, being that you are in a different country, but they might not be expecting yours. I've lived in many countries and have found that it takes a few seconds to adjust to whatever accent it is that I'm hearing. And if I'm in my home country, I'm usually not expecting a foreign accent and it'll take a second to adjust --- even if that accent is one I was quite familiar with while living overseas.

Sounds like people are just trying to be friendly with you when they say things like they like your accent, etc.; it sounds nicer than them being rude to you. Not really a problem. Most of them won't try to be your friends or follow you home. They may even see it as pleasant customer 'appreciation'.

I use my own accent wherever I am, but I will re-pronounce a word in the accent of the person I am speaking with if they didn't quite catch it the first time. Not such a big deal.

GL.

that sounds like a good tactic

A question for you.

When you were in the UK, did you learn every language on earth so that you could communicate with visitors, or did you expect them to speak enough English to get by?

You expected them to have enough English, right?

Is it not then arrogant of you to refuse to speak enough American to get by when you are here?

The only problem with me is, I have a strong Welsh accent and when I modify certain words the American way, I think I sound like a bit of a twit....

I use our local Subway (double steak American cheese on Italian herb and cheese - 12" of course)

I ask for everything just to avoid confusion, then throw the dog what I didn't want when I get home- everyone wins!! (she hates the banana peppers though)

LOL - An American accent will do you no good at our Subway!!

Spanish, or Punjabi might though

thats a good question.

Do you think that it offends americans in the same way the french get annoyed when you speak franglais?

difference is we do that TO offend the french!!

It's not like it's a totally foreign language though, is it? Saying tomahto or Chewsday surely doesn't constitute not knowing enough American to get by?
I admit though, there are just some words I cannot pronounce differently - wall, half, water... I can't say it American no matter how hard I try.

I can see changing the names of things to get by, but I see no reason other than convienience to change pronunciation. If you keep changing your pronunciation to the American English us Yanks won't really get used to hearing UK English and the problem will persist.

It might depend on your regional dialect as well. Just as an example, in my lifetime I've spoken to one English guy face to face. He had a very BBCish accent and I had no trouble understanding him. Then I watched the movie "Billy Elliot" and was constantly having to rewind because I couldn't catch it the first time.