Time for a wee rant. This'll only take a few seconds, I promise.
It really bugs me when I read or hear something like:
"Everyone can't be an astronaut."
...when the intended meaning is actually...
"Not everyone can be an astronaut."
Think about it. If everyone can't be an astronaut, no-one can be an astronaut, right?
So why do Americans (and I've only noticed this in American writing and speech) use language in this weird way?
And ... do all Americans do this, or just some?
If it's just some, I could then say: "Not all Americans misuse grammar this way." NOT "All Americans don't misuse grammar this way".
End of rant. As you were.