> What is the actual purpose of freedom of expression in a democracy? Is it being able to call people N-word online with no repercussions, or is it being able to organise, form political parties, and change the country?

What is the difference between the two? Because you're going to make a cultural argument and NOT a legal one. The C-word is one you throw around (and the Aussies to) but would cause an American woman be pretty upset. You seem perfectly fine with its use, but we frown on both terms socially but they are strictly legal.

Defamation VS political speech would be a better comparison, and I could make the argument that Americans being more lenient are better off with our freedoms.

From your list of purposes about freedom of expression, you're missing "the ability to criticize powerful individuals". If you cannot prove, in a court of law, that your statements are 100% true, you can absolutely lose your shirt in a defamation suit in the UK. It's so egregious that the US had to pass a law specifically shielding American free speech from the UK's libel laws. (to their credit, in 2013 they improved their laws substantially, such that you can no longer be found liable for provably true statements)

In the US, in contrast, you can say pretty much anything, as long as it plausibly enough true that the plaintiff can't prove you don't believe it. "Donald Trump is a child rapist" is an example of speech that would not be protected in UK courts. Sure, I can point at all his visits to Epstein's Island, and his running child pageant shows, and complaints made against him to establish that it's not unreasonable to believe it, but I cannot prove in a court of law that he did it. So in the UK, he would win a defamation suit against me. On the flip side, here in the States that is quite safe to say in a public forum. It's quite difficult to prove a negative, and even if they passed that bar, they would then need to prove to a court that I did not believe that statement.