I have to say, as a Brit I'm feeling like I'm less likely to remain a regular user of this site over time. I don't think so much it's the language/terminology issues - we seem to be managing perfectly well with everyone posting in their own local derivative of English, which seems in the majority to be American English (My only personal bug-bear is grilling & broiling in American English not being what I expect, and I have to make a conscious effort when reading these terms).
Obviously from a personal standpoint it would be easiest if everything was written in English, but I'm happy to research ingredient names or translate units as and when appropriate. In fact I reguarly do this already to some extent, considering I often use recipes from my girlfriend's native French (often written in Ch'ti to further complicate matters!).
What I do find difficult, however, is understanding posts that assume a US audience, or make reference to American culture as assumed knowledge. Things like assuming an ingredient will or won't be available, or that it will come in a given form (eg. In many countries UHT milk is the norm, whereas as I Brit I'm more used to HT/SL, flash-pasteurised, milk).
To summarise somewhat, I don't particuarly think we need to worry too much about ingredient names or units of measure - at the end of the day a salmon is a salmon, regardless of what you call it. What I do think we really need to be careful of are assumptions we make about where other users come from. Obviously some questions will have to be region-specific, but then I feel they should be tagged as such.
Other sites that I'm an active member of manage to make it easy for everyone, such as photo.stackexchange.com and of course stackoverflow.com, so I don't see why we can't.