Confused Identity

I can remember a conversation with Abby when she was visiting in Helsinki, and us using our normal jargon completely forgetting that James wouldn't have a clue what we were talking about! When mentioning TESCO my mind said superstore but we described it as 'like walmart'. Not that I have any clue what walmart is really like, just what I've seen on tv, which we know is always right ;-) and what other people have told me who have been there. I assumed it was near enough a good enough explanation. So I was horrified the other day when I drove past ASDA and it displayed 'part of the wal*mart family'. Since when?!?!?! Have I just been dizzy for the last...life...or have they just joined? There's an interesting story to the history of supermarket chains in the UK and how they developed but now they seem to be linking up over the waters so what is it now...British? or American?