First things first, calm down. There's no guarantee that the SITSA Act will be used to make kratom a schedule A substance even if it is not amended. Look into the Analogue Act which has been in effect since the late 2000's. It has the exact same wording as SITSA, minus increased minimum sentencing. If kratom were truly an analogue under that act and it's expansion, SITSA, it would already be illegal. The proposed amendment is more of a failsafe.
SCREEN does not make kratom illegal, it gives the FDA the power to seize and destroy substances from the mail as they see fit. If it passes unamended, we may see the FDA seizing and destroying kratom from the US mail, but kratom will not be illegal.