I think the person is referring to the state, but not the people or the environment.
The USA and the UK have strong patriotic currents which are entangled with their imperialist past and present.
I don't think anybody here thinks you deserve to die or claim this would be acceptable, random internet stranger 💜

I'm not going to mock you, comrade. Black humor is how we at hexbear deal with the crushing weight of the historical and ongoing crimes of the imperial core countries we come from. I can see how that might be jarring to an outsider.

I'm sorry, what @supafuzz@hexbear.net meant to say was "Another crackkka down, unlimited genocide on the first world"

(Other commenters are right though "death to America" or "from the river to the sea" are not calls to do ethnic cleansing - that is projection on the part of colonizers - it is a call to dismantle settler colonial states like Israel and the US. The jokes about sinking TERF Island come from the fact that they aren't technically colonizers there in the modern sense so they should just sink into the sea as there is nothing else to be done. Well almost nothing )