I always wonder with that kind of racist explanation, how the line of reasoning goes.
Suppose for the sake of argument, there's a place where everyone has 10 IQ points less, on average, than the West.
The Flynn effect is about 14 points over a few decades.
How do you square those things? Did the West not have a society a few decades ago? Is there some reason you can't have civilization with slightly dumber people? There was a time when kids were malnourished in the west, and possibly dumber as a result. Also, not everyone in society makes decisions. It tends to be very few people, and nobody thinks politicians are intelligent either.
I've never heard an explanation of intelligence that had any actual real-world impact on a scale that matters to society.
The explanation would have to have quite a lot of depth to it, as you have to come up with some sort of theory connecting how people do on a test to whatever you think makes a good society.