Yes, I think Manchester United's failure in their first two Premier League matches is a strong reason for Amorim to leave Manchester United. If left unchecked, Manchester United could face a much worse season. So, given this situation, I believe Manchester United must take decisive action. Amorim will have no excuses this season. As we know, Amorim has been given the freedom to sign any players he wants in this transfer window. But it turns out that none of that can change the fact that Manchester United is currently performing very poorly. So far, they have only managed to pick up one point in the Premier League from their two matches
Manchester United did shown some good changes in a first match with Arsenal and I consider it is a signal of their promising future with Ruben Amorim. They cleary did not get good results in two matches so far but it's not right to sack Ruben Amorim immediately as it only results in another crisis for Manchester United. Let's give him at least one first half of season, then can consider of sack decision around winter transfer season.
I still think that giving Ruben Amorim this full season to prove his ability is a best choice for Manchester United. If they don't do this, and sack him in middle of season, they will return to impatient approach in previous seasons and it's hard to convince other head coaches to join their club after Ruben Amorim.