My sibling comment understates the critique. There is no such thing as "average IQ". Countries don't IQ test representative samples of their population, so hucksters like Richard Lynn just make shit up and pull samples from mental institutions (where IQ tests are used, as they should be, as diagnostics).
This is a pretty simple and obvious observation. Have you ever been asked to take a proctored IQ test to help establish the "average IQ" of your own country? Presumably not. So why do people keep getting took by this silly idea that "average IQ per country" is a thing?
Possible conscripts are usually IQ tested in some way. If you have national consciption, then it would be a pretty good sample of the 18 year old male population.
Why the focus on Lynn?
Focusing on his critics is more illuminating and damaging to your presumed position:
Systematic review by Wicherts et al: "In light of all the available IQ data of over 37,000 African testtakers, only the use of unsystematic methods to exclude the vast majority of data could result in a mean IQ close to 70. On the basis of sound methods, the average IQ remains close to 80."
They of course follow it with the conjecture: "Although this mean IQ is clearly lower than 100, we view it as unsurprising in light of the potential of the Flynn effect in Africa (Wicherts, Borsboom, & Dolan, 2010) and common psychometric problems associated with the use of western IQ tests among Africans."
It's always curious how "common psychometric problems associated with the use of western IQ tests among Africans" don't carry over to economics and other things. Wouldn't you expect them to have similar problems with other western "ideas"? Also interesting how Easterners adapted to western IQ tests so well they are better at them than the West.