Kudzu....from China. Rapid growth overtakes and chokes native trees and shrubs, blocking access to sunlight.
Red fire ants...from South America. Aggressive and rapidly invasive all across the south.
Cane toad...imported to Australia to contain the grub on sugar cane. Toxin so poisonous that it has severly
disrupted the food chain, becoming an apex predator.
Boa constrictors...released as pets from households. Adapted extremely well to FL and GA. No natural enemies.