hasn’t hit this IQ wall

[Ostap]

As yet, the United States hasn’t hit this IQ wall — despite what you may be tempted to surmise from the current state of the political debate. But don’t rush to celebrate American exceptionalism: If IQs are dropping in other advanced countries but not here, maybe that means we’re not really an advanced country too much poverty, too little social support.

Opinion | Many developed countries are getting dumber, and the U.S. is likely next

An intelligence crisis could undermine our problem-solving capacities and dim the prospects of the global economy.

www.nbcnews.com

Hello everyone. What does the emphasized part mean? (I know what IQ means, the meanings of "hit ... wall" is unclear to me)

 

[Tarheel]

In this case, knowing the literal meaning definitely helps in understanding the figurative meaning. If you "hit the wall" literally, there is a likelihood of being injured. While you you probably won't be injured, if you "hit the wall" figuratively you will have difficulties that are hard (if not impossible) to overcome.

www.fraze.it.com

 

[teechar]

"Hit the wall" is an idiom meaning when one becomes unable to make progress in a particular field/activity.
Here, "Hit the IQ wall" means not becoming smarter/cleverer.