I watched a scathing retort from an American producer a few days ago. He was able to clearly explain why low skill manufacturing simply can not and will not come back to the US.
This is me paraphrasing, I didn't save the original...
1. Most of the manufacturing being done in China is being done by robots, and the people involved are the ones that program and run the robots. We don't have the robots here, the facilities to house them, or the trained people to run them.
2. The cost is just astronomically different. A skilled factory worker in China happily makes about $1000 a month, while a skilled factory worker here would complain about $5000. The tariff could be 500% and it would still be cheaper to produce in China.
3. It would take years, if not decades for them to move manufacturing to the US. In addition to the added payroll costs, there would be the money spent on building the facilities, robots, infrastructure... no matter what the tariff is, it will still be cheaper to stay where they are and just pass the tariff on to the consumer.
4. If they did try to relocate, there's no guarantee that the tariffs would be in place in 4 years. They know that they might end up investing billions unnecessarily... so they'll just wait it out.
5. Many of the materials needed simply don't exist in the US, so importing those materials (with tariffs) would just make it even more expensive.
6. When he quotes jobs across production companies, he said that he'll have replies from China within a few days that are ready to go! Compared to US companies that demand a much higher quantity, more work on his end, a much longer turn around time. All to get lower quality for a much higher price.