4chan is clearly operating in the US. The UK can easily cut the overseas cables and fix the problem!
If I offer a service in US I still have to respect US law, it doesn't matter that I'm based in Luxembourg or New Zealand.
The same applies in reverse.
E.g. many US news outlets never cared to implement gdpr and geoblocked European users from accessing their websites.
If my services are available in US, I need to comply with US laws as well.