I agree with FroFro. Fish and plants have a resistance (varying) to various pathogens that are present in their habitat water. These pathogens can often be very different in temperate regions from tropical and sub-tropical regions. Which means the fish and plants from the tropics may not be able to manage with the pathogens in temperate regions, and vice-versa. Of course, sometimes they do...and usually to the detriment of the local ecosystem. Fish and plants introduced into areas have decimated native populations. But my point here for your purposes is that the local plants may introduce pathogens the fish cannot deal with, as FroFro mentioned.
The other thing is that depending where you live, plants suited to your temperature year-round may not manage in permanent tropical temperatures. This too works in reverse. So plants from temperate areas when placed into a heated aquarium often die rather quickly, which can be a problem too.
If you were setting up a tank of native fish (local to your area) the local plants might work, though there is still the danger of transporting pathogens and microscopic critters. It is not always easy to somehow "treat" for these.
Many of these same issues can occur with wood taken from local water systems too.
Byron.