The larger question is, how is this even possibly a thing?
That there are legal liabilities that are wholly dependent on the internal emotional state of another person is absolutely insane. How is it possible to take a government that treats its adult citizens like kindergartners seriously?
Because that isn't the standard. Why do you imagine it is? There you are assuming that Brits are mentally enfeebled. Standard HN position.
Look, just because the USA draws this nice simple extreme bright line doesn't mean it's magically the right line or that it works particularly well.
There is a coupling between your obsession with absolute freedom of speech and your obsession with absolute rights to bear arms that leads to you arming yourself in arguments that could be resolved better over a cup of tea.
Racist language isn't just offensive, for example -- it reinforces racist conduct and can be seen in that wider context. There's no reason to assume there's a freedom to be racist in actions in a country that still has racial divides; I'm not sure why "speech" is excluded from those actions. It can rise to the level of harassment. Trolling and griefing is a massive social problem; free speech shouldn't protect you if you make someone's life a misery even only online with entirely broadcast speech.
We (sometimes! actually unusually!) deal with this at the level of misdemeanour (magistrates courts).
The USA has been known to prosecute jaywalking and can't even deal with swatting -- a means of using overkeen armed police who can only perform conflict resolution if they are armed like soldiers to potentially accidentally murder someone at distance -- so I think perhaps it's a little churlish to come after us because we in our crowded little country think being rampantly offensive to large numbers of people sometimes rises to the level of misdemeanour.