I was also...well, not surprised per se, but certainly annoyed to see that "Native American" in any form wasn't even an option. One could construe that as revealing, I suppose.

I don't know how relevant the question actually is, but if we want to track ancestry and racial, ethnic or cultural group affiliation, the folowing scheme is pretty hard to mess up:

Country of origin: <drop-down list of countries>
Country of residence: <drop-down list with "same as origin" as the first option>
Primary Language: <Form Field>
Native Language (if different): <Form Field>
Heritage language (if different): <Form Field>

Note: A heritage language is one spoken by your family or identity group.

Heritage group:

Diaspora: Means your primary heritage and identity group moved to the country you live in within historical or living memory, as colonists, slaves, workers or settlers.

<radio buttons>
European diaspora ("white" North America, Australia, New Zealand, South Africa, etc)
African diaspora ("black" in the US, West Indian, more recent African emigrant groups; also North African diaspora)
Asian diaspora (includes, Turkic, Arab, Persian, Central and South Asian, Siberian native)

Indigenous: Means your primary heritage and identity group was resident to the following location prior to 1400, OR prior to the arrival of the majority culture in antiquity (for example: Ainu, Basque, Taiwanese native, etc):

<radio buttons>
-Africa
-Asia
-Europe
-North America (between Panama and Canada, also includes Greenland and the Carribean)
-Oceania (including Australia)
-South America

Mixed: Select two or more:

<check boxes>
European Diaspora
African Diaspora
Asian Diaspora
African Indigenous
American Indigenous
Asian Indigenous
European Indigenous
Oceania Indigenous

What the US census calls "Non-white Hispanic" would be marked as "Mixed" > "European Diaspora" + "American Indigenous" with Spanish as either a Native or Heritage language. Someone who identifies as (say) Mexican-derived but doesn't speak Spanish at all would be impossible to tell from someone who was Euro-American and Cherokee who doesn't speak Cherokee, but no system is perfect...

If only White, how does the race change when one moves to another continent? And if White Hispanic, why not have also "Italic" or "Scandinavic" or "Arabic" or whatever other peninsula-ic races?

Because we don't have as much useful sociological data on this. Obviously we can start collecting data on any of the proposed categories, but if we're the only ones, it won't much help us figure out how LW differs from what one might expect of a group that fits its demographic profile.

Since I believe the question was intended to determine the cultural background of LW readers, I am surprised that there was no question about country of origin, which would be more informative. There is certainly greater cultural difference between e.g. Turks (White, non-Hispanic I suppose) and White non-Hispanic Americans than between the latter and their Hispanic compatriots.

Much of the difference in the example of Turks is captured by the Muslim family background question.

Offer a text field for race. You'll get some distances, not to mention "human" or "other", but you could always use that to find out whether having a contrary streak about race/ethnicity correlates with anything.

If you want people to estimate whether a meetup could be worth it, I recommend location rather than nationality-- some nations are big enough that just knowing nationality isn't useful.

Most LessWrong posters and readers are American, perhaps even the vast majority (I am not). Hispanic Americans differ from white Americans differ from black Americans culturally and socio-economically not just on average but in systemic ways regardless if the person in question defines himself as Irish American, Kenyan American, white American or just plain American. From the US we have robust sociological data that allows us to compare LWers based on this information. The same is true of race in Latin America, parts of Africa and more recently Western Europe.

Nationality is not the same thing as racial or even ethnic identity in multicultural societies.

Considering every now and then people bring up a desire to lower barriers to entry for "minorities" (whatever that means in a global forum), such stats are useful for those who argue on such issues and also for ascertaining certain biases.

Adding a nationality and/or citizenship question would probably be useful though.