Great question CDL, thank you for asking! The differences are plenty for astute mongers that have been in the game forever.
Asian American girls are easy to spot due to a heavy influence of western culture in their fashion, makeup, body type, instagram style photography, visible tattoos, lifestyle (pics in expensive cars, jets, beach, etc) Like most American girls in their 20s and 30s, Asian girls born and raised in america will be heavily influenced by the Kardashians. It is a very distinct style of makeup, fashion, plastic surgery. If an Asian girl has butt implants I would be willing to bet my house that she was born in america.
Contrast that with an ad from a "typical" kgirl. Most often you will see them wearing bikinis or lingerie. If she's wearing an outfit like a dress or school girl or whatever, it'll likely have a dated look. I'll get to the reason for that in a bit. Makeup will look more natural or more likely to have her face blurred out altogether. It's also a phenomenon for the face to have a weird photoshopped look, like possibly a poor attempt at placing someone else's face on another person's body. You don't see that with Asian American girls. Body type will almost certainly be slim or skinny, maybe athletic at most, as that is the preference in Korea, Vietnam, China, Japan, etc. Oh, I forgot about pale skin, another preference in Asian culture, as opposed to a healthy tan for all our caifornia girls. I don't know if I've ever seen a visible tattoo on a kgirl in her ad, even if she has one in real life. The reason for this and also the blurred or photoshopped face is because kgirls are highly cautious about being outed in real life. This is the reason why occasionally you'll see that the girl will not see men from their country of origin. Korean girls born and raised in Korea are far more likely to be heavily influenced by kpop and korean drama stars in their fashion, makeup, body type, plastic surgery, etc. Basically the polar opposite of what a Kardashian looks like.
Finally, the photography. Your typical kgirl ad is going to look more like an old school photoshoot. The fashion, makeup, style of photography will all have sort of a dated look. The reason for this is because most of the time the photos were taken 10+ years ago! You see, most kgirls started out as salon girls in Korea. The preference for salon girls is super young, so once they "age out" in their late 20s, they hop a plane for America and start working for the agencies here. They'll have a bunch of photoshoots done when they first start out at the salon, enough to last them all throughout their kgirl career. This is why so often reviews start out like, "I think she is the girl in the pictures, but I couldn't tell for sure." Often it is the same girl, the pictures are just 10-15 years old! Instagram beauty filters weren't a thing 10 years ago, so these ads will have a dated photoshop feel, while Asian American girls will use filters and photoshop technology far more advanced.
Anyways, it does feel great to spread some useful knowledge! It takes a big man to admit that he doesn't know everything about the kgirl scene and ask when he has questions. I think this is what they call progress! I'm proud of you!