Green mambas are NOT native to Florida. They are native to Africa. It probably escaped captivity during a hurricane.
An individual green (or black) mamba could survive in Florida quite well. Adequate food sources and a climate not that much different from their native Africa. While a stray mamba is clearly a menace, it is nothing compared to the situation if a breeding population of mambas get established.
I didn’t think they were native. after reading the story, I now wonder if “someone” has purposely imported it/them for just the purpose we are reading about.