Not quite the same thing since it was a school official rather than police, but we had something similar in the US. Right down to confiscation of a juvenille sign.
But police knocking on your door and confiscating your device because you called some politician an "idiot" by posting an online meme seems almost unthinkable in the US, when even the president himself is slinging insults like that at political opponents all the time.
My point is not that there is clear black/white line and the US have free speech and Europe doesn't, just that the free speech/defamation tradeoff is slightly different.
But your overall point - that not every population defines free speech the same way - is accurate. I think the difference here is just a bit less than sometimes implied.