Many WWII vets, particularly the ones that fought in the Pacific theater, had serious problem with the Japanese. Some Americans that lived back in WW2 have tension (some racism) between Japan because of what they did. All the cruelty that took place, Prisoners of war were tortured (burned alive, cut there body parts off), and so on ( propaganda). plus the account of pearl harbor which they also targeted american civilians.
The vast majority of those people are gone now.
Most Americans think of Japan as a place of technological industry and of strict(er) moral codes.
Also, the popularity of anime is rapidly growing in the U.S. and this gives the younger generations a link to Japanese culture. As of right now I'd say that the average U.S. citizen is neutral towards Japanese people, Theres still abit of negativity on Japan (things like bad past WW2,Toyota,) but in the years to come look for people to be much more positive towards Japanese.
@Knightrunner thats really funny
Well there was a transfer student, that came to my high school from japan last year. total opposite from your description. looked a bit too (Asian) He was a surfer ( his had was professorial tennis/surfer in japan) but he fit in quite well, I introduced him to like most of my friends (we all play sports and stuff like football) and loved it here. He went to a gifted school for smart kids and he said he HATED it there, to strict, parents wouldn't let him hang with friends most of the time, and what ever. Just boring. little to no fun. I noticed over the course of his year here, he became more laid back, here. He wants to come here in America for College, and I told him he can stay with my family for a month or so, cus we have plenty of guest rooms in my house. We still talk over facebook today