Let me put it this way.
The hottest girls in America clear Japan by a longshot, not even close. You'll hardly run into supermodel looking girls in Japan.
The average Japanese girl clears the average American girl by a longshot. Very rarely do you see a Japanese girl below a 7 or 6, there's little variance. It's overall a country of beautiful women.
Korean girls lose on average and in the upper scale. Though I will say in terms of peaks, you're probably more likely to see girls that look like supermodels in Korea than Japan.