H1Bs risk deportation when they are fired. It is inconceivable for this to not impact their performance and behavior. Combine that with Amazon's Jack Welch style stack rank and firing of the bottom and it becomes even worse
Do you have any evidence that this has ever happened? It's a big company so I assume it's something that's demonstrable. I happen to think that it's unlikely that Amazon leadership would adapt by making allowance, rather than replace.
Many visa workers have families, and relocating an entire household, especially when children are involved is a huge emotional and logistical challenge.
Its not easy