To be honest, I still do not fully understand what the claim is. Amazon has 3 segments: US, Europe and AWS. Its 10-Qs/10-Ks disclose all of the information that is required by US GAAP w.r.t what information should be available for a segment.
Is the claim that simply stating "The entirety of what happens on the Amazon website in the US is one segment" is wrong? What subsegments would you want to see?