Living in the Philippines the past few months has taught me that the differences in measured intelligence are very real. In one world IQ chart the US is listed as 98 and the Philippines 86, which is similar to Mexico. The differences do appear that great, but are magnified by the extreme poverty and terrible education system here. I suspect that 86 is not even a representative sample.
A racist acquaintance of mine likes to ask Filipinos how many weeks are in a year. Not once in over 20 times I have seem him ask this did anyone know the answer, although one woman guessed 48 after multiplying 4 x 12. That in itself is amazing as most Filipinos struggle with doing simple multiplication like that in their head. Most businesses insist on sales staff using calculators when they do not have a cash register that handles it.
On the other hand, kids can pick up a smart phone and figure out how to use it very quickly, no different from the states from what I can tell. And, bar girls are every bit as good as manipulating customers to make money as strippers in the states.
At this point I am not even sure that IQ tests are a valid way of measuring intelligence. The effects of poverty, terrible education, and the general lack of interest and incentive to exercise the mind are so profound here, it would be extremely difficult to figure out all the causes for differences in IQ. and assign reasonable numbers to them.
I still stare at the world IQ map from time-to-time and wonder, how can that be?