It never left. The US manufacturing output steadily increased from the 50's to the recent recession. Right now, it is at an all time high. The idea of american manufacturing being shipped overseas is just false, and I'm sick of people repeating it.
What happened is that as wages got expensive, US labor was replaced by machines where possible, and by some cheap process steps overseas where not possible. Intel CPUs are a good example: They used to be made wholly in the US, employing a lot of blue-collar workers. To save costs, the factories were automated to the point where the only process steps left that employ a lot of people without advanced degrees are packaging and testing. And then those were shipped to Malaysia and Costa Rica. The high-capital process steps that create most of the value in the system are still in Oregon, Arizona and New Mexico.
Manufacturing jobs, as they used to be, are gone. Not because of globalization, but because of robots. And the old kind of manufacturing jobs will never return -- it just doesn't make sense to pay people $30 a hour for what could be done faster, cheaper and better by a robot.
A buddy of mine made a mint working as a welder building fabs in Phoenix when they were leaving California in search of cheaper water and lower regulations. He was very worried about the toxic emissions and very lax (non existent) oversight.