The map you posted does not give any reasons for the disparate IQs seen in different countries. It does not give methodology for how it came up with “average” IQ.
What I see on that map is that there is a high correlation between countries where everything about the environment—malnutrition, infectious disease, lack of early childhood enrichment—inhibits proper brain development, and the average IQ (however it was determined). I also see little correlation between the racial composition of various countries and their average IQ. For example, all of the countries across the north of Africa and the Middle East, as well as India, are all majority populated by Caucasians. But they aren’t doing so well, either—therefore, it must be the culture and environment working to suppress the effect of the genetic components of IQ.
I seriously question the placement of China and Mongolia among countries with the highest average IQ score. I suspect that there is some misinformation involved, because the government of China has a strong interest in presenting a good public image.
Perhaps you should compare the average academic and economic achievements of Indian and east Asian children of immigrants to the (non) achievement of the children of mestizo or African immigrants. In both cases, the children experience poverty and "outsider" status. In the first case, they generally climb out of it in a single generation. In the latter cases, they typically stay there or sink ever lower.
“What I see on that map is that there is a high correlation between countries where everything about the environment—malnutrition, infectious disease, lack of early childhood enrichment—inhibits proper brain development. . . . “
What I see is someone in denial.
Does China's influence extend to fudging the IQ scores of Asian-American children, who score higher than whites? Are malnutrition levels among American blacks worse than the Vietnamese peasants who came here from the rice paddies of SouthEast Asia as children and became valedictorians?