While always causing a heated debate, Asians generally score higher on average than Americans on IQ tests (Among white Americans, the average IQ, as of a decade or so ago, was 103. Among Asian-Americans, it was 106). I would argue that Asians aren't by in large more intelligent, but that they eat better and get more exercise.
See the recent study: The new five-year study of more than 2,200 adults claims to have found a link between obesity and the decline in a person's cognitive function.
Since 3 out of 4 Americans are overweight, what we are probably seeing in these IQ tests are diet and lifestyle in action on the national level.
And yes, I too agree that IQ tests aren't all they are cracked up to be. However, go to a Chinese buffet and look at the thin people in the restaurant. They usually work there. All the Americans are large, with plates piled up to the ceiling full of food.