Looking at the wiki page, PISA seems to have some criticisms, one being it seems very gameable. I'm not really familiar with it.

It might be interesting to try and find some more objective support of my claim, and I'll try and post anything worth posting, but anecdotally...the difference between the US and other developed countries is night and day. It's so incredibly easy to run into people in the US who genuinely astoundingly lack the basic knowledge that in other countries it is taken for granted that adults hold.

There's a reason other countries talk shows don't have segments like asking random pedestrians to name any country, literally any country on a world map, so they can laugh when they fail.