Import cane toads to Australia to eat beetles. Import Kudzu into the American South to stop erosion. Import English Ivy because it's pretty. Import nutria to Louisiana for a cheap supply of fur.
Say it with me, kids: No natural enemies. Let that be a warning.
Sort of like the snakeheads in Maryland and other eastern areas. They are reproducing faster than authorities can kill them out, thanks to some one who introduced them to some area ponds.
"Import English Ivy because it's pretty"
If it makes you feel any better, American nurserymen returned the favor by exporting American ivy to Britain...American poison ivy. It didn't exist in Britain until then.