I don’t know that any of those things back up your claim that the ‘average’ American is smarter than the ‘average’ European. It definitely suggests that the top Americans are better than the top from anywhere else but how are you measuring average smartness? This website (https://worldpopulationreview.com/country-rankings/education-rankings-by-country) puts the USA 31st in education rankings. This one (https://www.datapandas.org/ranking/education-rankings-by-country) has them 15th (in 2022). This website (https://worldpopulationreview.com/country-rankings/average-iq-by-country) puts them 33rd by average IQ. This one (https://international-iq-test.com/en/test/IQ_by_country) puts them 30th. Admittedly you did say controlling for race but that doesn’t seem to be option in any of my quick searches but based on this is doesn’t appear that the ‘average’ American is smarter than the ‘average’ European.