"This is something which we call.." is the kind of phrase you use to introduce the reader to a new concept for the first time. e.g. standing in a line in a shop is something which we in the UK call "queuing". You could make it shorter by saying : "standing in line is known as / called queuing in the UK". It has the same meaning.

You could subsitute 'what' for 'something' here: in something (which) the US government calls ... in what the US government calls ...

Thank you for pointing it out.

Your question should be: What is the meaning of "something" in this sentence OR What does "something" mean in this sentence.