Bootable USB created on Mac to format PC
This won't work as you noticed. 

I'd recommend using unetbootin from https://unetbootin.github.io/. Just follow the instructions there or use the instructions from the ubuntu page (https://www.ubuntu.com/download/desktop/create-a-usb-stick-on-macos)

If you want to use the command line, do e.g. (MAKE SURE TO REPLACE WITH THE CORRECT PARTITIONS!)

hdiutil convert -format UDRW -o destination_file.img source_file.iso
diskutil partitionDisk /dev/disk2 1 "Free Space" "unused" "100%"
dd if=destination_file.img.dmg of=/dev/disk2 bs=1m
diskutil eject /dev/disk2