Not technically, no; they aren't native to North America.
They have been introduced to lots of different places though, either by irresponsible aquarists, or on purpose as a natural form of mosquito control, and left to breed on their own, they would most likely revert to a more wild type.
There are many feral populations of guppies in Texas. Although they are not truly wild, they are also not easily confused with aquarium varieties. Those fish can be treated as if they were wild types TheFishGuide. If you have some, give them tank parameters similar to those we give to domesticated guppies and they should do just fine.