When I was discussing how I had been playing around with Census spreadsheets, a friend of mine suggested I find places that are the closest, ethnically speaking, to the United States as a whole.
This wasn't too hard to do--I just downloaded the full Census tables for states, counties, and Census-Designated Places using Social Explorer. Then I compared the ethnic distribution for each one with the ethnic distribution of the country as a whole (using vector distances). Then I just ranked each spreadsheet from smallest to largest by this "Americanness" measure. I know the electoral relevance of this is rather indirect, but it might help you get some visual picture of the country as a whole. Also, a lot of people at DKE are interested in demographics in general. I think this has not been done before (at least, nothing comes up when I Google the top three census-designated places).
The results, however, sometimes confirm what you might be thinking--that this is a silly exercise. But in case you're curious:
States: The top five states were:
1. Illinois
2. New Jersey
3. New York
4. Connecticut
5. Florida
Counties: The top ten counties were:
1. Rockland County, New York
2. Hartford County, Connecticut
3. Fairfield County, Connecticut
4. Arapahoe County, Colorado
5. Seminole County, Florida
6. Will County, Illinois
7. Polk County, Florida
8. Richmond County, New York
9. New Haven County, Connecticut
10. Nassau County, New York
Here's where this starts feeling like a pointless exercise. Rockland County, New York is ranked number one by at least one other metric:
The county has the largest Jewish population per capita in the country, with 31.4%, or 90,000 residents, belonging to the Jewish faith. Rockland also ranks 9th on the list of highest-income counties by median household income in the United States with $75,306 according to the 2000 census.
There's nothing wrong with that, but it starts making "looks like America" sound like a pretty hollow claim. Also, I am from Fairfield County, and let me assure you that it is pretty damn atypical of anything.
Cities: I'll do two lists here. First, the top ten Census-Designated Places:
1. Travis Ranch CDP
2. Seffner CDP
3. Wichita city
4. Four Corners CDP
5. Roswell city
6. Mansfield city
7. Fitchburg city
8. Wylie city
9. The Acreage CDP
10. Manchester CDP
If you're like me, the only other one of these you've heard of, other than Roswell (insert conspiracy-themed joke) is Wichita. But basically, if we were a city (and Census-designated ethnicity was all that mattered), we'd be Wichita.
Let's look at cities with a 50,000 population or more (I recall a Wikipedia article that looked at ethnically-unusual cities and broke them down in a similar fashion):
1. Wichita city
2. Roswell city
3. Mansfield city
4. Rowlett city
5. McKinney city
6. Wichita Falls city
7. Fort Smith city
8. Wellington village
9. Sarasota city
10. Port St. Lucie city
Finally, following that Wikipedia article, here's cities with a 100,000 population or more:
1. Wichita city
2. McKinney city
3. Wichita Falls city
4. Port St. Lucie city
5. Denton city
6. Omaha city
7. Palm Bay city
8. Arlington CDP
9. Worcester city
10. Topeka city
I haven't included the actual breakdowns, but by construction, they're all close to the U.S. break down of 16.35% Hispanic, 63.75% non-Hispanic White, 12.21% Black, .73% American Indian, 4.69% Asian, .16% Native Hawaiian, .2% Some Other Race, and 1.93% Two or More Races (at least as reported by the 2010 Census--see http://factfinder2.census.gov/). If you have any questions about actual breakdowns, feel free to ask in the comments. When I am less exhausted, it might be fun to try to add income or education or Obama% or something to the extent I can.