For others interested, this doesn't seem to be fully accepted. A few studies in EU countries (and Australia)) have shown slight regressions from past increases.
No studies done in the US which is the cohort here.
Studies have been done in the US. Here [1] is (to my knowledge) the latest, and it does indeed show a substantial reversal of the Flynn Effect. And to my knowledge the reversal of the Flynn Effect is indeed globally acknowledged. The debate at this point is on the cause.
The main reason early studies were in places like Scandinavia is that they have compulsory military enlistment alongside IQ tests, whose results are made available for research. Studies in places like the US came later, because simply getting a representative and comparable sample is non-trivial. There's also the cultural issue that studies on IQ are walking on eggshells in the US.
And it's not slight regressions. We've gone from gradually and consistently gaining IQ, to the current scenario where some studies [2] have shown declines as great as .29 standard deviation per decade. Meaning in 40 years we'd all be a whole standard deviation away from where the mean used to be. That is exceptionally disconcerting, particularly if it doesn't just flat-line at some point.
No studies done in the US which is the cohort here.