The census data is absolutely useless to medical researchers. "Black" doesn't describe anything about an individuals genetic code other than melanin content. The genetic variation among "black" people is as great or even greater than the genetic variation between any given black person and white people.
Then why do researchers routinely find a link between race and various health conditions?
Race may be a social construct with no genetic basis, but social constructs are real, and often have medical consequences.
"Asian" is used by the census generally to describe anybody from about Pakistan eastward, lumping Indians with Koreans, Japanese, and Chinese, all of which are very distinct from each other.
...and, surprise surprise, this is why question #9 in the 2010 Census form doesn't have a checkbox for "Asian" (contrary to what you imply); it has separate checkboxes for Asian Indian, Chinese, Filipino, Japanese, Korean, Vietnamese, and Other Asian--with a write-in box for people to write in their ethnicity in the latter, complete with a list of examples (Hmong, Laotian, Thai, Pakistani, Cambodian).
So you're very much wrong about the Census lumping "asians" together.
And what constitutes "black" and "white" today, anyway? Is Tiger Woods black, asian, or what? Are his kids black or white? Do you want to bring back the old "one drop" test, so if any of your ancestors are black, you are deemed black?
It has been absolutely clear for decades now that the answers to the census questions about race and ethnicity are about the respondent's self-identification and their identification of the other people in their household, not some objective adjudication of their "real" race. The upsides and downsides of this, its (un)reliability and its problems are very much a matter of public discussion.
Again, race is today understood as a social construct, and race is very much a matter of personal identity. What race people identify themselves as is a significant fact about the population. Nobody who's not constructing a strawman is pretending that this data is to be treated as any more than what it is.
Demographers are among those who continue to insist that we define our society by skin color, so I don't feel much need to help them out.
I'm sorry, but the American society is very much defined by skin color. Native-born and raised black people, whose ancestors have been in this country no shorter than the majority, overwhelmingly live in different neighborhoods, speak a distinctive dialect, have different artistic expressions, have different naming customs for their children, have worse health, are discriminated against in housing, health and employment, and a host of other differences that would not be possible if the nation's culture did not see them as a different race in the first place.
I also put American for race.
Thank you for completing and submitting your Census form. Your answer will be routinely adjudicated as "Non-Hispanic White," perhaps after some minor statistical controls to estimate the very small number of non-whites who fill out "American."