I think you guys are talking past each other and missing the point, anyway. This thread was based on the premise that the character Mei is Chinese but
@derekiscool thought she looked American. It's really not about whether or not she actually IS Chinese, but rather what she looks like she is.
I personally think she looks like she could be from most places in the world based on looks alone. Does she look like a stereotype? Not like any I'm aware of. That's a good thing.
Is she believable as an American? Absolutely. As a Chinese? You bet.