Let's move on to something that really weirded me out. How Mr. Efron looks. Is he Asian? Nope. Does he have a scar on his face? Nada. Does he have crazy anime hair? Kinda...
Actors can change their look for a film. This is the lovely Charlize Theron. This is her plus fifty some pounds and some make up. Won the lady an Oscar. Well... She's a highly talented actress, but that's besides the point. You don't look at the lady on the left and think "Oh serial killer". I don't look at Seth Rogen and go "Oh he must be playing a super hero in an up coming film", but he is. Looks are so one dimensional and subject to change. Mickey Rourke is a great example. Just because he doesn't look like Sousuke Sagara walking doesn't the street doesn't mean he can't look close to him after he sits down in an artist's chair for a few hours.
Full Metal Panic's plot can lend its self to be set in almost any country. Can it be done in the USA? Yes! You can totally set this movie in a US town. How about... The Ring? Based off of a Japanese film, but watching that movie for the first time when I was twelve I wouldn't have known it. The setting, the plot changes all worked well to make that movie translate well to an American audience. Can Full Metal Panic do the same? I believe so. I really do. However, the giant robots miiight give it away. So the actors, given the right setting, don't necessarily have to be Asian.
(On a side note, the upcoming Avatar: The Last Airbender Movie's setting is in an Asian backdrop, hence my little bit of outrage due to the white washing of the cast. It's all about setting when it comes to casting.)