American IQ scores have rapidly dropped, proving the 'Reverse Flynn effect'

IQ hasn't been beneficial to evolution for over 100 years. Once means-tested welfare came into existence, being low-IQ became more advantageous. The reason Europe was able to take over the world is that they taxed the poor (low-IQ) more than the rich in the dark ages and the rich out-bred the poor for at least 2 generations.

Very arguably social welfare resulted in the biggest increase in IQ levels in history as general health, nutrition, and education improved. Also social welfare improved social mobility which should cause IQ to have more of an impact rather than less of one.

I am not rejecting this point but I have a hard time accepting it Carte Blanche. If anything if IQ is lowering for generic reasons I would suspect birth control as a cause especially since it’s a more recent phenomenon than means tested welfare.

One of the first European world powers after the dark ages, Portugal, was not more advanced than many of the areas it attacked except for in weaponry since Europe had been infighting while other math and science was being pursued in eastern parts of the world. Regardless of what percentage of motivation you ascribe to "we want their shit" vs "we want them to take our religion," I don't think you can say it was an advantage or motivation driven by intelligence.

("The rich outbred the poor" also seems very dubious, labor was still very manual, so you gotta have someone to do it.)

Social welfare could do BOTH things - dramatically increase IQ for the next generation (that grows up with proper nutrition etc) while also remove the selective pressure that increased IQ over the course of centuries.

Social welfare hasn’t been centuries. Many social welfare programs have barely been 1 generation. The big ones (social security, food stamps) aren’t even 1 century old!

Portugal was advanced at being the geographically westernmost mainland European country, and at fighting with the Moors for long enough to adopt lateen sails.