What nationality are you, anyway?

In the United States there is more space where nobody is than where anybody is. That is what makes America what it is.
--Gertrude Stein

I have recently been workin' retail part-time, at a big box bookstore whose name starts with a B--I'll let you all deduce it from there. I keep telling myself that it'll fund an opera ticket, someday, which helps. Cashiering is tedious (with a bit of excitement when a customer yells at you), but it also can be kind of funny, and my co-workers are a nice bunch. And I've gotten asked multiple times by them,

"What nationality are you, anyway?"

It's a common ice-breaker in these parts, where there are so many recent immigrants. But it's stumping me. My first instinct is to say "American," but what does that even mean? It's like how my English flatmates were very dubious that I wasn't secretly Canadian. "But, I thought you wanted universal healthcare?" they'd say. "You don't talk like a Valley Girl! Where is your gun?" Perceptions of Americans...is that what makes us who we are? Is that why my knee-jerk reaction is to mistrust everyone from Texas?

To illustrate my dilemma, here are some conversations I had a few days ago with some co-workers (while we were waiting to be yelled at by customers, no doubt).

Co-worker 1: Hey, what nationality are you?
Me: Oh, mostly Swedish with some Dutch and English in there somewhere.
C-w 1: I totally thought you were Croatian.
Me: Really?? (note: I have never been thought of as being from somewhere remotely close to the Mediteranean. My ancestors probably put on sunscreen at the mere thought of Croatia. Perhaps my tan is better than I thought...) I'm not, but I've heard it's beautiful.
C-w 1: Me too. How long have you lived here?
Me: In the city? About 2 months.
C-w 1: Wow, your English is REALLY good.

and

Co-worker 2: (after going through the what-nationality-are-you thing, and how-long-have-you-lived-in-Brooklyn thing) You've lived a lot of places!
Me: Well, not really...just a few places in New York. (18 years in Jtown, 4 years in Gtown, 3 months in England, 3 months here, a fair number of East Coast-ish states visited..is that a lot? It's never seemed so to me.)
C-w 2: Well, I moved to Brooklyn from Bangladesh when I was 2, and I've never left.
Me: Never left? At all?
C-w 2: I guess I went to the Bronx once, and Manhattan a few times. And Connecticut, but I was asleep the whole time.

At the same time that this struck me as so strange, it also kind of makes sense. Why WOULD you leave, when every culture and good and service that you could possibly want is here? It could be argued that they've seen more and done more staying in Brooklyn than I ever have. So could someone just identify as "New Yorker"? My family has been in this country long enough that I don't have intimate connections with the Mother Country, but I still feel a strong allegiance, and the culture is part of who I am. Should I even feel that allegiance when I speak more Spanish than Swedish? What happens when/if those "old" traditions are erased, subsumed, Americanized? How, and why, do you identify yourself when you're closely tied to two countries? What makes us American? What nationality are you, anyway?

Just some general unanswerable questions for a Wednesday night.