Yawn. North America during the last glacial maximum killed off most of the tropical fauna and vegetation. Now that we are in an interglacial there are a lot of empty niches for tropical animals to fill.
Between exotics and uninterrupted vegetative succession, our property was down to 60 plant species. With careful management and control of exotics, that number is now 400.
Exotic species are the single most powerful force causing mass extirpations, more than development. Yawn all you like, but the rate of differentiation will never match the rate of displacement.