Globalism shuffled jobs around the world, and trade policies can change that to a modest extent -- one's trade policy can't change the fact that your citizens are too expensive versus Thailand or China. Tariffs against Mexico cannot make a Shenzhen. GM is not metaphorically coming back to Detroit.
US manufacturing employment is going down, and even if / when high tech manufacturing brings production back to the US, it will be robotic production. And with every company in the world racing for machine learning, I don't see how the future looks good for a specific generation of people in history too old to newly take up a globally competitive trade. Also, it's been mentioned around here that driving is one of the most frequent jobs in most states in the US, and that Uber recently made a deliver of beer by automated truck. Uber and every relevant company in the world is trying to destroy a category of worker from everywhere in the world.
Tariffs can absolutely change the fact that your citizens are too expensive. You can argue that the consequences are not worth tariffs, but you can't say that they don't promote production in your country.
The only way for a rich nation to have metaphorical Shenzhen is if they're okay with Shenzhen-style citizens. Tariffs can't make it more attractive for Foxconn to move their factory plans to the US. I'd also say that worker discontent is one of the major sources of Trump support, but the last thing they want are the ecological reasons for making Shenzhen an attractive manufacturing capital. You need an environment where laborers cannot even fathom leaving or engaging in collective bargaining. China is okay with a scenario where much of the nation profits from the backs of abused workers because they have the might to quash malcontent. In a democracy where these abused workers have voting rights, this translates to instability.
The decentralized nature of the economy also makes it so that an overly internal strategy like tariffs are insufficient. If the US stops buying from China altogether, China is still the manufacturing pit stop of the world. The rest of the world has no reason to coordinate the tariff strategy with you. Only your nation artificially sees increased prices. It's even worse if your nation ups production but nobody wants to buy it because it's too expensive. Your production isn't a power unless you export, and tariffs alone won't make you export.
Manufacturing businesses want an environment where (1) citizens are dirt cheap, (2) citizens can be legitimately abused, (3) government is stable and amenable to these practices, (4) the country is connected to global supply chains so you can integrate that country as part of your production system.
Also, if / when manufacturing does come back to the US, I imagine that it will bear the fruits of every company racing towards applied machine learning. It will be robotic labor that outscales cheap labor.
I agree that manufacturing jobs are now automated, so they aren't coming back. But your other points are not true - imagine the US halted all imports. If you halt all imports, companies either produce in the US or don't sell to US consumers - it doesn't matter what labor costs. With tariffs US companies don't have to compete with dirt-cheap international labor. Whether or not this is a good idea is debatable, but you can definitely use policies to promote domestic production.
If you want <exports>, with tariffs, US companies still have to compete with dirt-cheap international labor. This is what I meant by improving production but not production that <exports>.
Because when you export, you're once again selling on the global market. You must compete with all players. If you can't export, if your manufacturing machine is too expensive, or if your output is too non-unique, then you aren't creating the fertile atmosphere of Shenzhen. How is this going to increase export to generate more American wealth?
Having a production machine that makes things only for your nation and nowhere else is just a redistribution of money. Redistribution of money can be very healthy, but why not just do it directly without potentially wasteful intermediary processes?
Also, I mentioned the point of Shenzhen style abused labor manufacturing vs. robotic high tech labor, and that if manufacturing comes back to the US, it will likely be in the form of robotic manufacturing, and it's not obvious whether this manufacturing will have much room for the masses of unskilled workers.
Manufacturing never left the US. Manufacturing in the US is doing just fine. It is, however, as you suggest, automated to a degree that means manufacturing jobs left the US.
US manufacturing employment is going down, and even if / when high tech manufacturing brings production back to the US, it will be robotic production. And with every company in the world racing for machine learning, I don't see how the future looks good for a specific generation of people in history too old to newly take up a globally competitive trade. Also, it's been mentioned around here that driving is one of the most frequent jobs in most states in the US, and that Uber recently made a deliver of beer by automated truck. Uber and every relevant company in the world is trying to destroy a category of worker from everywhere in the world.