Don’t confuse the wasabi that we get in the States for actual wasabi. Nicer restaurants will have it, but you’ll probably have to ask for it.
Would be interesting to verifiably taste real wasabi. Who knows, maybe I've never actually even tasted the real thing?
They give you a root, and a grater. Tastes milder than what we get, here.
I have heard that it is impossible to domesticate (has to be harvested wild, on certain mountains). However, I watched a program, where a guy in Hawai'i said he'd figured out how to domesticate it.
Haven't heard much about that, though.
Here is a decent paper that discusses the challenges[PDF]:
https://www.skagitmg.org/wp-content/uploads/Public-Pages/Foo...
To have it the spiciest you should wait a good ten minutes or more, the spiciness is activated by the process: "The chemical in wasabi that provides for its initial pungency is the volatile compound allyl isothiocyanate, which is produced by hydrolysis of allyl glucosinolate [...]; the hydrolysis reaction is catalyzed by myrosinase and occurs when the enzyme is released on cell rupture caused by grating" (adapted from wikipedia)
You can taste the difference but in most contexts it is pretty substitutable with the fake wasabi, hence the ubiquity of the latter.
You can absolutely buy some wasabi powder that is made with up to 50% real wasabi on Amazon fairly cheaply, but what you're tasting is still going to be the horseradish. They're basically just selling you the discarded remains of wasabi that isn't actually any good anymore. Still safe to consume, but stale, essentially.