Americans just aren't there to do all these jobs. It's not that Americans aren't willing it's just that we have other things we do. Just what are all these potential fruit pickers doing now? Of the 5.9% that's currently unemployed most are going to be boing back to some sort of white collar work in a little bit, others will find work in nice air conditioned stores. Then you've got your people who wouldn't work if you put a gun to their head.
You can try raising wages but eventually it's just not worth it and businesses are forced to close taking other jobs and investments with them. That's part of the reason why some of us here think a "kick the bums out" policy without a guest worker program is doomed to either fail or cause a recession.