The origins of the wasabi horse-radish (preferably from the Izu peninsula), miso paste (preferably from the Nagano mountains) and pickled ginger (preferably from Tochigi) will all be scrutinised. Rice is expected to be the most frequent area of failure: a true sushi master will insist on Japanese koshihikari rice grown in Japan.
The same variety grown in California might, just, be acceptable. Faux pas may include serving Chinese soy sauce, or miso soup in a porcelain cup.Meanwhile, bluefin tuna used in sushi has been found to contain terrifying amounts of mercury, at least in the US.
It's an interesting idea. I've been eating Japanese food and using chopsticks since ~1982 here in Melbourne (tender age of 6, my parents liked Japan), and I've seen huge changes in the availabilty and quality of Japanese food here in Oz.
The crazy part is that I don't think that Australian's actually care or want authenticity with their food culture - sushi (well, (australian) temaki sushi (californian rolls), and it's mutant cousins) is the new sandwich - cheap, easy, fast, relatively healthy. And as you can see from that qualified sushi definition, we are so far from rice paddy's for it not to matter :)
A fair percentage of our Japanese restaurants have Korean or Chinese staff/ownership from what I can tell, and at least one of those is in my top ten for authenticity (takashimaya, smith st, caveat: their "soba" is terrible)
What has been good to see in Melbourne recently is the Koreans stepping up and opening _Korean_ restuarants. Kim Chi!!!!!!!! My favourite is "Kim Chi BBQ Grandma" on Collins st... I'