I'm sure they don't look directly at immigration status when deciding who to lay off, but they do look at their expected pay and benefits, which just so happen to be strongly correlated with immigration status more often than not.
replyThe expected pay and benefits of anyone in a FAANG firm have everything to do with their level. Within levels, the bands are fairly narrow.
replyAn L5 SWE performing at S gets paid about the same, and receives the exact same benefits, regardless of their status.
Actually, scratch that, the H1B is often awarded an extra benefit - sponsorship and legal fees for converting to a green card.