The question is, what do those limits on speech really add?
For example, Germany has extremely stringent limits on hate speech. In fact, it goes beyond that, and gives courts the authority to outright ban political parties, and even informal associations, that promote certain political ideas (e.g. any form of government that is not a democracy), even if such promotion doesn't involve hate speech per se: https://en.wikipedia.org/wiki/Streitbare_Demokratie. They have a robust enforcement regimen, too.
And? They still have neo-Nazis marching in the streets (and, I must add, in far greater numbers than anything that happened in US to date). And they have AfD, which continues to grow in popular support, and to gain seats on both federal and regional level.
I would argue that in that regard, Europe and US inadvertently did a useful experiment: one side went all-in for free speech, another side decided to enshrine "intolerance of intolerance" in law. Looking at Europe today, I would dare say that the result of that experiment is that political censorship is a failure. It's not that you can't do it - clearly, there are many countries that do it quite successfully, even today. The problem is, all those countries are very heavy-handed about it - they don't wince at punishing people for being suspected subversives, for example. And so we call those countries dictatorships and tyrannies. But the amount of censorship that Europe decided it can afford while still retaining free society is fairly trivial to work around, and therefore ineffective. It's basically just security theater. It lets politicians point at all those laws and say, "See, we did something about the neo-Nazis! You're safe!" to their voters, even as said neo-Nazis openly march in the streets.