An analogy :
Prime minister , ministers are members of Parliament .
Suppose the prime minister say this in an MP meeting :
" Ramasamy become one of us "
he mean , Ramasamy become a MP , not another PM or equal to PM.
At the same time PM is still a MP , of course with higher power.
In the same way, GOD is an angel with highest power. If this explanation didn't satisfy you, then please read " us " as " residents of heaven " .
I wrote the following lines in reply # 14
If " us " refer to Trinity , then , did Adam become a member of Trinity ? Not at all . He became as one of the residents of heaven .