When installing the Curt Trailer Hitch # C13271 on your 2016 Fiat 500X you will not need to drill any new holes in the frame rails - metal - of the vehicle, as shown in the linked instructions. However, this hitch requires you to enlarge existing holes with a die grinder, or file.
Please note the Curt hitch is going to require the use of stabilizing straps # 18050 with all non-trailer accessories such as bike racks and cargo carriers in order to maintain the warranty. I've added a link... view full answer...