The US city that has the best Japanese food is New York City.
New York city boasts a wide variety of different great Japanese restaurants, which include high end sushi spots to even ramen bars and much more.
New York City has a large Japanese community that contributes to their diverse culinary scene.
Los Angeles is also known for their strong sushi presence and they also have some good Japanese foods.
Even Japantown in San Francisco or even Little Tokyo in LA also have excellent Japanese food.
And a lot of the restaurants in Japantown and Little Tokyo also have Japanese staff.
California also has some good sushi restaurants and serve some great nigiri, sashimi and even hand rolls.
And even Seattle, WA also has some great Japanese food and restaurants.
A good Japanese restaurant in Seattle, WA is Onibaba by Tsukushinbo which is located at 515 South Main St, Seattle, WA.
I've eaten the food there when I was in Seattle WA a few years ago and the food was delicious.