Comments on nationality from my friends and co-workers:
1.
Me (in French): “Adama, look what I made last week!” (points to charts and schematics I drew up and posted on the wall)
Adama (in English): “Oh, wow. You are definitely an American.”
2.
Laetitia (one of my roommates): “But the NGO is paying you, right?”
Me: “Nope. I’m an intern.”
Laetitia: “What?? You work on Saturdays, but they’re not paying you???”
Me: “That’s correct.”
Laetitia: “Oh, wow. You are definitely not French.”
3.
(after spontaneously joining a card game being played by some guys sitting on the corner:)
One of my new buddies: “Where are you from? You’re French, yes?”
Me: “No.”
Buddy: “What?”
Me: “Guess.”
Buddy: “…German?”
Me: “American.”
Buddy and his buddies: (laughing) “No. You’re not American. You don’t have….the shape of an American.”
Me: “Why? Cause I’m not fat?”
Buddy and buddies: “Right!” (all laughing)
4.
Laetitia again: “When did you start learning French?”
Me: “Sixteen years ago, at school.”
Laetitia: “Wow! But why did you choose French?”
Me: “I don’t know. I just always wanted to learn it.”
Laetitia: “Really? I can’t understand why an American would want to learn French. We are the most…comment dit-on, impoli?”
Me: “Rude.”
Laetitia: “Yes, we are the most rude people there are.”
Me (laughing): “You are the most self-hating French person I have ever met.”
Laetitia: “But it’s true!”
Still No Such Thing, Again 
Funny! Your French must be very good if they thought you were French!
No, definitely not. It’s more that most people find it impossible to believe an American could speak French.
Très drôle!
I see that the wall charts are in French. Maybe that’s what confused them.