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

"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.

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.