> Shouting FIRE in a full venue

"Crowded theater"? In any case, yes, that's a popular understanding of limits on free speech in the US, but it's actually been superseded twice - first by "clear and present danger," then by "inciting or producing imminent lawless action." These days, it's probably (I am not a lawyer) legal to yell "fire!" in a crowded theater under many circumstances.

> Sadly, the recent developments in US show pretty well how freedom of speech cannot be measured by "How many specific laws are there about things I cannot say?".

There are no laws preventing you from saying anything in the US, unless you are specifically, directly inciting people, at that moment, to do things that break other laws. That's the point. You can't measure it in terms of degrees of restrictions; the US has none, and all European countries have at least some. The latter approach opens the floodgates to restrictions on any kind of speech that the government doesn't like. The US Constitution prevents that from ever happening.