The most important difference between this and Kim Dotcom is the US has a lot of weight to throw around, evidently having enough to lean on the governments of small countries like NZ. In the case of 4chan though, it's a once-great but now relatively minor country trying to have their way with an American company, meanwhile America has laws explicitly for the purpose of telling the British to fuck off with the imposition of any of their free speech violating antics against Americans.

The US entertainment industry has a lot of weight to throw around.