The singer currently lives in the Californian city but revealed via Instagram it hasn't all been beaches, sunshine, oceans and fun.
Katie said: "You know you're in LA when you have a gun pointed at you whilst you're stuck in traffic! TERRIFIED!! NEVER LEAVING MY HOUSE AGAIN!!"
She added: "#StopGunCrime #BanOnGuns."
Katie later said: I just want to get back to London! It's crazy how accessible guns are out here in the U.S.! Education and laws need to be tightened!"
The 29-year-old appeared on the seventh series of X Factor, where she was mentored by Cheryl Fernandez-Versini and finished in seventh place.