What do you think is going to happen to the price of McBurger when employers have to pay $15 per hour? What will happen to people making $15 now? I sure as hell will be asking for a raise even though I'm far away from minimum wage. Anyway, this is a separate topic from J-1 kids. 
J-1 is a federal program, just like H1-B is, and many others. If you think these are not fair to the american people, then go ahead and make your vote at the presidential election this fall. Build a fence, deport everyone, then see who shows up for work at the fields and fish processing plants. By the way, have you ever stepped inside a fish processing plant? I have, and now have a lot of respect for people working there 14 hour days. No wonder they employ J-1's, nobody else wants to work there.