The reason is that they all generally have that refined Korean celebrity look and because of this we assume that they are all Korean. All the best K-Pop quizzes in one place. Thats what I heard Sunny - SNSD born in LA but grew up in Kuwait in the Middle East Amber - f x Woosung - The Rose.
If youre in LA keep an eye out for these stars.
For those unaware of who Joshua from SEVENTEEN is hes a vocalist for the popular K-Pop group. Moon Hyung Seo or Kevin Moon is a Korean-Canadian idol born in Vancouver Canada. There are more K-Pop idols that hail from LA than you might expect. Names like KAACHI and Oli London are pretty familiar to fans and are often criticized and not actually considered idols by many but there are likely a lot of names on this list you havent heard of.