I'm not at all mixed up. I have heard of many Polish (and other European) children moving to the U.S. and having to be moved up a year because they were more advanced than their classmates.
This used to happen in Canada too. Two kids of my sister-in-law, went through it in 1990s.
The research you quoted is to be expected in the richest, and one of the most populous countries in the world. By the way, these universities buy in a great deal of their expertise from abroad by offering European and Asian academics contracts they would be nuts to refuse.
There is also another factor:
Ivy League American universities are very good, many state universities are just average, but all are judged on the same number of criteria, which are not available in Poland, such as money, laboratories. Poor standing of Polish universities have many causes - one is dispersion of resources and publications. For example, in Poznań alone there are six state universities: Classical (where I studied), Technology (where I taught), Medical, Economical, Life Science, Fine Arts and three state colleges: Music, Physical Education, Banking. Add to it about 20 or so private colleges at various level.
If you collect all the publications from all the six state universities, the number will be several times higher than when taken separately.
I bet that would be easily comparable with the total output from all faculties of both Toronto universities: UofT and York.
It's probably a better indicator to look at the median levels, e.g. reading age and overall literacy and numeracy in the general population. I know it's anecdotal but when I read website forums the worst English I read is usually from the U.S. btw, I'm not anti-American.
2009 results from junior high schools (15 years old) around the word, as provided by Programme for International Student Assessment (PISA):
Math: Poland 25, USA 30
Science: Poland 19, USA 23
Reading: Poland 15, USA 17