The southern region has produced the most American gold medalist from 2000 - 2016 but it's by far the largest region so this is to be expected. On a per capita basis, the Western region is the most successful. However, no region is vastly over or under-represented compared to population. The northeast could be described as the least successful though. 

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For these chart, multiple medals for 1 athlete at each games are counted once. For example, Michael Phelps has won 23 gold medals over 4 games. So he is counted 4 times when making the chart. This is so 1 dominant Olympian in a multi-event sport doesn't skew the measurement of how well regions and states produce athletes. However it would also be wrong just to count athletes once if they are successful over many years. 

Although the south is the place of birth of more black American gold medalists than any other region, it is actually underrepresented since over 50% of black Americans come from the south. The Midwest is the most successful per capita in producing black Olympic gold medalists since 2000. 

Among white Americans, the south is significantly over-represented in producing Olympic gold medalists since 2000. Michael Phelps was born in Baltimore, Maryland. He has won 23 gold medals over 4 games. The west is also over-represented for whites.