I would like to see actual scientific studies demonstrating that any exotic plant has successfully "invaded" a genuinely pristine ecosystem and disrupted it. All of the plants you mentioned have "invaded" areas that were or are disrupted already by human activity. If you can find a true pristine ecosystem that hasn't been disrupted by humans now or in the past, then you can research this question. Otherwise, I suggest refraining from the panicky hyperbole that is more characteristic of pseudoscience than reasoned research.
Even in island situations (for example, a fresh volcanic island barren of plant life), all the plants and animals that colonize it are "exotic". How can they be "native" when there are no native flora on such a new volcanic island? Yet they come, colonize and, over time, establish a balanced ecosystem, unless humans come in and disrupt it.
For further reading, see "Invasion Biology - Critique of a Pseudoscience" by David Theodoropoulos
http://www.invasionbiology.org...
