Being thin doesn't mean a kid is starving to death. It just means they're skinny. Both my wife and I were very skinny as kids; luckily, she still is.
The US has an ethnic mix very different from Europe's. Native Americans and Pacific islanders tend to get fat on Western diets. Southeast asians and filipinos tend to be small and thin. The distribution will still be close to normal (you can't avoid the central limit theorem) but will be wider than in an ethnically uniform population.
But if the below-2-sigma part of a population is defined as malnourished, then all populations have equal proportion of malnourished.
The children who die of malnutrition in the USA are overwhelmingly victims of profound illness, generally birth defects. One rarely reads, say, of a lunatic parent who allows a child to die from lack of care. We have AFDC, food stamps, free meal centers, charities, and child protective agencies that look out for kids. Far more dangerous is being killed by trauma, overwhelmingly likely to be inflicted by a step-parent or other non-blood-relative.
But what is this obsession with US juvenile nutrition? It's a weird, recurrent theme.
John