|From left to right: USA, Japan, Netherlands, and France|
More here. The authors of the studies quoted ascribe the height of the Dutch to better early medical care and diet, but don't seem to consider the ethnic mix present in the US (but not in The Netherlands) as significant enough to mention:
The Dutch have some of the world's best healthcare, particularly at the stages of life that really make a difference for how tall we end up -- prenatal and the early years of childhood.
Second, they spread the health around. The most well-off Americans are tall, but less-privileged groups across all races bring down the average.
Our waistbands drag us down, as well. By eating so much, we produce too much growth hormone, too early in our lives. And so we stop growing earlier than the Dutch, who eat lots of protein like milk and cheese, but not too much.