The US is the exception in the sense that it is the only country that has seriously tried to narrow down these limits to what is absolutely necessary.

Obviously not. "Seriously" and "absolutely necessary" are subjective terms, essentially matters of personal opinion, and plenty of Americans argue that the limits in the US are either too loose or too rigid (see the current debates around social media, Section 230 and whether or not private platforms should be forced to act as common carriers.)

Meanwhile, cultures differ, and people outside of the US may well see their own governments' drawing the lines elsewhere, for instance banning of hate speech and Nazi propaganda, as "absolutely necessary."

Yeah, this attitude that what sort of limit is absolutely necessary is "subjective", "essentially a matter of personal opinion" is exactly what the US (not every single american, but american first amendment jurisprudence) is the exception to.

It really isn't, even the Supreme Court has differed on the matter over time.

To differ doesn't mean to accept that something is subjective. Even mathematicians have differed about proofs.

> To differ doesn't mean to accept that something is subjective.

Yes it does. That's what subjective means.

Obviously, many people refuse to accept that their personal opinions on political matters are anything less than absolute, immutable, objective fact, but that isn't relevant, because refusing to accept that doesn't make it, or you, objective.

>Even mathematicians have differed about proofs.

Politics isn't math. There is no equation or statement that can quantify the American model of freedom of speech, nor prove it correct, much less more correct than all other models, in the same way as E=MC^2 or Pythagoras' theorem.

See: https://www.cs.umd.edu/~gasarch/BLOGPAPERS/social.pdf