appps, There are feral chickens in the US in some locations. There are several areas in Hawaii with feral chicken populations, both Key West Florida and Fitzgerald Georgia have feral populations that are celebrated (sometimes and by some) in those communities. Some small communities in Florida have some as well as the large cities of Miami and New Orleans Louisiana. I have also read of a group of feral chickens surviving near an off ramp of a highway in southern California.
Their status as a problem depends on the individuals perspective. If you look at you tube and search for feral chickens you can find many videos of them.