The perception is vis-a-vis the perception of economic, social and political status.
Continuing with the pun on the title, everyone expects more from America and America in turn also expects more from itself. When they hear "FWIW, Poland and the USA get very similar results from their K-12 systems" they can say "Oh good for Poland. This used to be a communist country and now it is as good as US in Education" or they can also say "Holy crap. America is now on par with an Eastern European country that was ruled by communists just couple of decades ago, how sad, we could do some much better".
Now, note, I don't endorse this binary view. I want all the countries to have good education, especially my country.
Also, I grew up in Eastern Europe and can also say that my high-school education there emphasized math, physics, literature and English (or other foreign language) a lot more than my American high-school (I also went to an American high-school for a one year btw, so I can compare a bit). I came to US in the 10th grade and was taking math courses along with high-school seniors and tutoring them. I was only above average at home in those subjects.
Overall, what I think works well for US high-schools:
* Kids have a choice already to specialize because they can each take an individualized curriculum. Some took more literature and English some took more physics. That's great.
* Frequent and objective testing. A lot of objective testing and quizzes. Keeps you on pace.
* More approachable and more informal teachers. Teachers that care seem to be really good. Yeah there are the ones that don't. But I noticed in my other high school even teachers that cared acted pretty un-approachable and just showed their care by signing you up for math and physics contests (Olympiads) we call them.
What doesn't work well for US high-schools:
* Too many what I see pointless after-school activities, too much emphasis on sports. Are all these kids going to become professional athletes. So why are they spending all afternoons bumping into each other at high speeds and getting injured.
* Social scene is fucked up and detracts from learning. Because there are so many activities and so much individualized choice on what classes to take. People form cliques and end up being not very approachable. There isn't a group of people you get to know and spend your whole day and years with. There was just less drama and mental effort spent on who is friends with whom and who cheated on whom.
* Too much emphasis on passive media aids (video) for teaching. There was a lot of "here watch this video kids".
* Too much emphasis on group projects. On a certain meta level they are great because it teaches everyone how group function and don't function. How to take advantage of others and how others get to take advantage of you. There were very few times when groups are evenly matched and everyone puts a fair share of work and end up with a great result.
What doesn't work well for East European high-schools:
* Corruption to the core. Everyone cheats. Teachers take bribes. Principles take bigger bribes. Kids cheat from each other. Those that don't cheat get left behind because those that cheat make the exams and test look like a piece of cake, so those get harder and harder ("Oh so it looks like everyone in this 10th grade knows about derivatives so well. Let's bring on the double integrals then!")