Why is fent so popular in America but non existent in Australia?

As an avid Australian drug user I'm curious as to why I've not seen fent once. Seems like Australia is 95% meth and weed 5% prescription pills. Anyone know why our market is so lacking? I know it's mainly cause I'm in Perth and eastern states has more diverse tastes but yeah just don't understand how something so popular in America hasn't caught on here.