Penguinn,
I've lived (or worked in for extended periods) a lot of places in the US.
Where I felt short at 5'7.5:
South Dakota
North Dakota
Minnesota
Iowa
Nebraska (except Omaha)
Illinois
Where I felt very average in the US:
Texas
Oregon
Washington State
California
Colorado
Wyoming
Montana
Utah
Nevada
Florida
Specific cities I felt most comfortable in, height wise:
Omaha, Nebraska
Seattle, Washington
Vancouver, Washington
Los Angeles, California
San Fransisco, California
Dallas, Texas
Houston, Texas
Austin, Texas
Denver, Colorado
Miami, Florida
Portland, Oregon
These are all large diverse cities with larger Hispanic, Asian, and Indian populations.
By far my favorite area in the country is the Pacific Northwest, which is Washington State and Oregon. I personally will be moving to Vancouver Washington in the near future, as it is very close to both Seattle, WA and Portland, Ore, but is a much cheaper place to live than either of those cities.