what is an american?

I've had two run-ins with the definition of american. Recently, one of my friends, in a room of with a mexican american, filipino american, and me (japanese american) and the dialogue was as follows

him: "i just realized i'm the only american in here."
me: "no you're not."
him: "yes i am"
me: "i'm american too."
him: "no. you're japanese."
me: "i'm just as american as you are."
him: "well you know what i mean."

let's remember that i'm a 4th generation american. my family has been in america for over 100 years.

in another one of my friend's assignments, there's a statement that says "I'm not white, I'm american."

This is stupid because the two are not mutually exclusive.

Here's where people get confused:
Ethnicity=The county of your ancestors. (My ethnicity is Japanese)
Nationality= The status of belonging to a particular nation, i.e. citizenship. (My nationality is American)

Let's be clear that ethnicity has nothing to do with nationality. Let's also remember that American has nothing to do with being white.

Don't let yourself appear ignorant and think that only white people are American.