The problem is not that the manufacturing left the US shores but that there is nothing worthwhile that can replace it momentarily and that creates unemployment. In the distant past agriculture was the main occupation. Then came the industrial revolution, today 2-3% of the population is enough to feed the whole country and also export a remarkable amount of food.
Same happens now in the industry. Less people can produce just as many products as in the past leaving a lot of people on the side. It certainly does not help that other countries compete with lower wages and less environmental regulations, but that is not the main problem. The main problem is that we simply do not need as many workers as in the past. No useful and viable jobs have yet been created to absorb the surplus workers.
The market is trying to create new occupations, like personal shopping assistants personal trainers, and other weird things but the amount of these new jobs is not enough. Maybe we need a lot more teachers, more artist more guides who knows. But this is the direction I think things will evolve.