The only people to move entire factories, were basically the Chinese a couple of decades ago or more. Would the Germans move an entire factor, like the Chinese did? I would think no.
Would German companies build new factories in America? I would think not likely.
What probably will happen in most cases is the factory closes, or they just continue muddling along.
The Italians have a lot of industry. None of it moved en mass to America the past 20 years, when that economy has been stagnant all this time.
The idea that German factories will move to America, seems to me one of those ideas promoted by the American enthusiasm and optimism. Like how they said they would be greeter as liberators when they invaded Iraq to topple Saddam Hussein.