You nailed the issue: "American teens are perceived as not being [good workers]".  That's not a perception, for the vast majority of American teens that is reality.  Mommy and Daddy coddle them until they are 26, as they spend their formative years staring into a smart phone and not developing social skills or a work ethic.  American teens opened the door for J1 workers.  Employers are not at fault.  American parents and their inept kids are the fault.