Prepared Uni (not live) in the US can come from Maine, Canada, Alaska, California, Chile, Japan or elsewhere. Although Japanese uni can be great, I still like California uni the best. Maine uni tends to be the smallest and it varies in color quite a bit. Alaskan uni has been quite dark lately but it has good flavor. Canadian and Chilean uni is somewhere in the middle range.

Live uni from CA tends to be the best here in the US because it is easier to keep it alive to the table (less shipping involved than other Pacific uni) and it seems to produce the largest lobes. I've opened green Maine uni and found very little inside, but some of my California uni has been packed full, generally in the early autumn.

Ensui uni, if that is what you had, Lori, is supposed to be uni that has been packed in salt water to maintain the impression of freshness.

There is also a type of uni preparation called Vana, which apparently is related to the Hawaiian word for sea urchin, but the Vana preparation that I know is generally made from all of the sea urchin that doesn't qualify for individual lobe sales - in other words, all the broken and squished pieces are packed together, often frozen, and then thawed out for eating or cooking. I've been served uni with scrambled chicken eggs, risotto, etc. and I wouldn't be surprised if there is someone that mixes it with grits in the South, but if so, Vana would be a much cheaper alternative than top quality full lobes from Santa Barbara...

If you get back to Tokyo, look in on my friend Yasuda, who moved from New York City a few years ago for the challenge of competing with the best sushi chefs in the world, but don't ignore Sushi-Sho if you can get in. Sukiyabashi Jiro is of course the most famous spot because of the Jiro video/documentary but if you don't want to spend that much money, you can do very well by just going to Tsukiji at 3AM for the tour and eating at one of the local restaurants that are a few feet away. I don't recall the names right now, but you can probably Google them for current reviews.