I consider myself a connoisseur of fine sushi and I agree with most of what you said.

Wasabi can be found in the US and its grown in the northwest. Just like Shiso, that little green leaf that is often placed under Ika.

Most traditional Japanese do eat Tuna, but not as sushi, they traditionally eat it as Sashimi (sans rice) or preserved in soy sauce (salt)

Most of the rolls we get here in the US are not traditional, most of the time, traditional Japanese diners eat Maki (rolls) that are simple, not this Salmon, cream cheese, onion mixture that we here seem to like (yuch!)

If you really want to impress your local Sushi chef, don't put extra wasabi on the top of the Nigiri, or mix it in with the soy. Most traditional sushi eaters simply dip the fish side in the soy sauce and pop it in their mouth. The Wasabi is mostly for mixing into the soy sauce when you're eating Sashimi. Nigiri has wasabi between the fish and rice.

There are lots of wonderful traditional Japanese traditions and foods that are part of the sushi experience. Unfortunately most Americans are too squeamish. (Their loss and My gain!)

Some day ask for Ika-Shiokara (or sometimes just Shiokara) or Ika-Nato. One of my favorites is Yamakake (Yamaimo or Japanese Mountain Potato grated to a slimy consistency mixed with Maguro and a little soy)