"That’s why we have these low wage jobs where you can walk in with no experience and earn some money. "

No we have these low wage jobs solely because a service or product is in demand and it requires someone to provide the service or product.

"The authors make it look like these kids are being abused and take away jobs from the Americans, which is far from the truth."

No again. The author reports that some J-1 employees are being abused and by definition all of them are taking jobs away from Americans because the jobs are in America. 

Just because a job goes unfilled at x wage/condition doesn't mean no one will do the job. As the pay goes up or the conditions improve more folks will show up to do the job. That is unless you find a source of folks that come from a place where the money/conditions you are offering is better than what they can get in the place they come from.