America's schools are no better and no worse than other nations. You get what you take out of schooling. Some just try to pass and move on without trying to actually learn.
It is more the person and not the school. With that being known and the fact that America accepts folks from so many nations..... we can move on to where are the folks from. How many are French, German, and etc.
There are dumb folks everywhere. All you have to do is turn on the news to get your fill. 
Denial is a wonderful thing, isn't it, too bad it leads to utter BS.
Yes, if you don't try, you won't learn, duh!
The reality is that it has to do with the parents and the parents putting pressure on their kids & the local school systems to perform as well as often giving money to fund more & better programs (such as AP classes etc..). Its very easy to find large discrepancies between public schools (in the US and elsewhere).
That being said, more motivated students coming out of "Gymnasium" in northern Europe tend to graduate knowing much more math than students in the US. That being said, they split the children between the ones who they think will be 'sucessful' and 'not successful' artificially inflating the success of certain institutions as well as allowing them to teach more in a shorter period of time (As the kids are more motivated).
In summery, no Schools across the country are not equivalent, nor are they equivalent to the rest of the world, it must be looked at individually on case-by-case basis.
