I am not a lawyer but isn't this expressly forbidden by the Constitution in Article I, Section 9, Clause 5?
> No Tax or Duty shall be laid on Articles exported from any State.
Last I checked China is not a US state.
It's a revenue tax on items exported from Taiwan to China by a US company. I don't think it counts as a US export at that point. Ignoring that it's illegal for the president to impose taxes at all.