Yup: "If we want to prevent America from suffering this fate, we’d better figure out why IQs are dropping elsewhere. … A range of studies … have found declining scores across Scandinavia, Britain, Germany, France and Australia."https://www.nbcnews.com/think/opinion/iq-rates-are-dropping-many-developed-countries-doesn-t-bode-ncna1008576 …
Read the article - it's very plausible as the main reason Importing violent, low IQ foreign men changes the culture on the margin. New culture has lower reproductive returns to intelligence across the board. Low cooperative env means lower returns to IQ