Invasive subspecies rarely have an effect limited to their conspecifics.
From another thread, but it applies here:
The European subspecies behaves completely different than the American subspecies and replaces not only its conspecific, but creates huge monocultures replacing whole communities of native wetland plants in North America.
The thing to remember is there are many processes (e.g., extinction rates, climate change) that do occur naturally in moderation, but anthropogenic activities have sped these processes up beyond what is “natural” (outside of mass extinction events, which admittedly have also been “natural” historically).